“The earth belongs to Him, He gives it to whomever He wishes and the eternality is for the pious people.” 
This correspondence took place at the end of the 10th year from Hijra. When the Messenger of Allah passed away, Musaylima found an opportunity to gather some followers around himself. He used to compose rhythmic prose to imitate the Qur'an and recited the prose for his followers.  Furthermore, he had told people he had exempted them from saying morning and evening prayers. 
Also, Sajah, the daughter of Harith Tamimi , claimed prophethood but after meeting Musaylima, she married him. It is said that as Sajah's marriage portion, he exempted the people from saying morning and evening prayers.
In al-Futuh we read that when Sajah met Musaylima, she said, “I heard about your excellent traits and chose you. I have come to be your wife so that we can both be prophets, and together, make the world obey us and be our subordinate.”
Musaylima said, “For your marriage portion, I exempted your nation from saying prayers at dawn and dusk.” 
When Muslims went to Yamama with an army led by Khalid Ibn Walid, they came across some of Musaylima's followers and asked them what faith they were in.
They said, “ãäÇ äÈí æãäßã äÈí
” “We have our prophet and you have your prophet.”
It was then that a war broke out between them. The Yamama battle was one of the bloodiest wars of Muslims with claimants of prophethood and apostates. In this war, the Muslim army lost a great number of its men, 58 of whom were from the Muhajirun and the Ansar and 13 men out of them, had fought in the Battle of Badr.  Ibn A'tham has put the number of Muslim martyrs at 1200 people, 700 of whom had memorized the Qur'an. 
In a text attributed to Waqidi, we read the details about the war and the many pre-battle bragging of the Prophet's companions, including 'Ammar Yasir. Immediately after the battle ended, Khalid married Muja'a Ibn Marara's daughter, who was one of the conspiring heads of Banu Hanifa, and indulged in his own lust and pleasure. Observing this, Muslims wrote a letter to Abu Bakr and said,
ÃÊÑÖì ÈÃäÇ áÇ ÊÌÝ ÏãÇÁäÇ æåÐÇ ÚÑæÓ ÈÇáíãÇãÉ ÎÇáÏ
“Do you please with our blood in dryness and this man keeps on living in relief in Yamama.”
The news reached Abu Bakr and 'Umar said, “Khalid always does something which pains our heart.” Abu Bakr wrote a strong-worded letter to Khalid. When Khalid read the letter, he laughed and said he was sure it was 'Umar's work because he knew Abu Bakr was satisfied with him. 
Another claimant of prophethood was Tulayha Ibn Khuwaylad Asadi. He also gathered men from the tribes of Ghatafan and Banu Fazara and tried to compose rhythmic prose to claim prophethood and stand against the Medina government.
In a battle between his men and the Muslim's army, 'Uyayna Ibn Hisn and his tribesmen from Banu Fazarah were defeated heavily and Tulayha fled to Damascus. Thus, another revolt was suppressed.  'Uyayna Ibn Hisn had repeatedly shown his enmity towards Islam during the life of the Prophet (S) but had finally embraced Islam. However, his presence in this current showed that he, like many others, had never believed in Islam truly.
When he was brought as a captive to Medina, people taunted him and said, “O, enemy of God! Did you become an infidel after converting to Islam?” But he swore he had not believed in Islam even for a moment.  Abu Bakr pardoned the captives of this war. Tulayha, too, came to Medina at the time of 'Umar and repented.
'Umar told him, “How do you expect to save yourself from hell when you have killed Thabit Ibn Arqam Ansari and 'Ukkasha Ibn Mihsan Asadi?”
Tulayha said, “God had wanted martyrdom for them and I did not kill them with my own hand, so there will be no hell for me.” 'Umar liked his reasoning and pardoned him.
Apart from claimants of prophethood, some other tribes became apostates in the basics. There is no doubt that the situation was prepared for apostasy but it is not clear for sure who were the real apostates and who are those who did not accept the Medina government merely for political or religious reasons. 
For example, one such group was Malik Ibn Nuwayra's clan who were accused and killed mercilessly undoubtedly just because of Khalid's personal issues and his mean moral motives. This is a blot of shame for Khalid and those who defended him. They considered his crime in massacring a number of Muslims and his adultery with Malik's wife after her husband's murder as a wrong interpretation of Ijtihad. 
Hearing about this, 'Umar was seriously incited against Khalid and asked Abu Bakr to oust him but the caliph called him the “sword of God” and refused to do so. 
Among the tribes considered to be apostate, there were some people who did not believe in Abu Bakr's caliphate and favored the government of the Prophet's Household. They said Abu Bakr had no “allegiance” to them so there was no need to obey him. They believed that the Muhajirun and Ansar had prevented the Prophet's Household from coming to power out of jealousy. 
According to Waqidi and Ibn A'tham, a clan from Kinda in Haďramawt was all apostates. Ziyad Ibn Lubayd was responsible for collecting tax alms in the region. Some men of the tribe agreed with paying tax alms while others did not. Once Ziyad chose a camel belonging to Ziyad Ibn Mu'awiya as tax alms, he asked for help from one of the influential men of Kinda named Haritha Ibn Suraqa and asked him to return his camel and take another one.
Haritha made the request from Ziyad but he did not accept. So, Haritha himself went among the camels set aside as tax alms and brought back Zayd's camel, saying, “We obeyed the Messenger of God as long as he was alive.” “áæ ÞÇã ÑÌá ãä Ãåá ÈíÊå áÃØÚäÇå
” “Today, we will obey anyone from his Household who comes to power.” Abu Bakr has no right of rule and allegiance upon us.
It is said that Ziyad Ibn Lubayd fled from the region overnight and composed poems terming the tribe as apostate.
He said, “We will fight you to make you obey Abu Bakr until you give up infidelity and apostasy and say you shall never return to infidelity.”
Of course, not all tribesmen thought like Haritha. What is important is that all of them refused to pay tax alms to the Medina government because they considered it humiliation for themselves. They believed in distributing tax alms among the poor within their tribe.
Some people of this tribe used to say, “We swear by God that we have come to be enslaved by the Quraysh. First, they send Muhajir Ibn Abi Umayya or Ziyad Ibn Lubayd to collect tax alms. Then, they threaten to fight against us.” 
Ash'ath Ibn Qays, from this tribe, said, “I don't think Arabs would accept the rule of the Banu Taym and leave the men of the Hashimites.”
He said in his poems, “If the Quraysh are to leave the power into the hands of Banu Taym and distance themselves from Muhammad's Household, of course, we are prior to it because we are the descendants of kings.”
Elsewhere in the above narration, we read that Ziyad sent the tax alms camels to Medina along with someone and he, himself, went to a tribe of Kinda named Banu Zuhal.
An influential man of Kinda named Harith Ibn Mu'awiya said, “O, Ziyad! You ask us to obey someone who has no accord with us.”
Ziyad said, “You are right. He has signed no agreement with you, but we have selected him to rule.”
Harith asked, “Why did you take the government away from the Prophet's Household when they deserved it, because God has said, “æóÃõæúáõæÇ ÇáúÃóÑúÍóÇãö ÈóÚúÖõåõãú Ãóæúáóì ÈöÈóÚúÖò Ýöí ßöÊóÇÈö Çááóøåö
.” “Some relatives are given more priority over others.”
Ziyad answered, “The Muhajirun and the Ansar know the interests of their government better than you.”
Harith stated, “I swear by God, it is not so. You did it out of your jealousy. I cannot accept that the Messenger of Allah has passed away without assigning a successor for himself. Go away from here.”
'Urfaja Ibn 'Abd Allah, another man of the tribe, said, “I swear by God, Harith is right. Expel this man from this place. His master is not eligible to be the caliph and the Muhajirun and Ansar are not better than the Prophet (S) in knowing the expediency of the government.”
Ziyad went to Medina and said, “The people of Kinda have revolted and have become apostate.” 
Ibn A'tham's further explanations on the disputes among the people of Kinda and Abu Bakr reveal their problem was Abu Bakr's caliphate. Making his mind to fight the Kinda tribes, Abu Bakr summoned 'Umar and said, “I want to send 'Ali Ibn Abi Talib to fight them because, ÝÇäå ÚÏá ÑÖÇ ÚäÏ ÇßËÑ ÇáäÇÓ áÝÖáå æÔÌÇÚÊå æÞÑÇÈÊå æÚáãå æÝåãå æÑÝÞå ÈãÇ íÍÇæá ãä ÇáÇãæÑ
“He is just and acceptable more to the public because of his excellence, valour, kinship and knowledge as well as his handling of affairs.”
'Umar said, “You are right. 'Ali is as you say but I fear one thing. I fear he may refuse to fight them. If he does not go to war, no one else will do so unless with disgust.” 
This discussion and 'Umar's consultation with Abu Ayyub show that there were some people among them who opposed fighting Muslims.
The caliph considered these things instances of apostasy, and historians have recorded these fights as the battles of Radda. These wars may be justified as necessary tactics for safeguarding the government but it is hard to prove the tribes' apostasy. When Abu Bakr decided to fight these tribes, some of his men, including 'Umar, objected to his decision. Later on, 'Umar said he opposed Abu Bakr's decision in the beginning but after some time, he learne that caliph was right.
The question was whether or not these tribes were apostate and if fighting them was permissible or not? Abu Bakr believed in their apostasy, so he even took their women and children captive and brought them to Medina.  It seems that 'Umar, like many Muslims, agreed with fighting them in principle but did not believe in their apostasy. According to Shahristani, it was because of this belief that 'Umar freed their captives  when he became the second caliph.
Another problem was that even if the tribes were apostate, many considered it illegitimate to take captives from apostates. 
There are numerous documents at hand indicating that some tribes were considered apostate because they refused to pay tax alms. For instance, a group of Yamama people believed in the principle of paying tax alms but refused to pay tax alms to Abu Bakr.
They used to say, “We collect tax alms from the rich in our tribes and distribute it among the poor and needy among ourselves, but we will pay nothing to whom the Book and traditions have not recommended him.”  Ya'qubi, too, writes, “Some people only refused to pay tax alms to Abu Bakr.” 
As mentioned earlier, 'Umar opposed the idea of apostasy of these tribes. According to Ibn A'tham, when Abu Bakr wanted to kill the captives of the battles of Radda,  'Umar said, “These people believe in Islam and they swear about it. Imprison them for the time being to see what happens next.”
Abu Bakr jailed them in the house of Ramla, daughter of Harith. After Abu Bakr's death, 'Umar told them, “You know what my opinion was about you. Now, you are all free without any ransom. Go wherever you want.” 
Qays on behalf of 'Asim Minqari was commissioned by the Prophet (S) to collect tax alms from his tribe. After the Prophet's demise, he collected the tax alms but instead of giving it to Abu Bakr, he distributed them among the poor in his tribe. This was considered as a criminal act. Even a proverb was made in this regard which said “More criminal than Qays be 'Asim.” 
Ibn Kathir, too, has reiterated that many Muslims refused to pay their tax alms to Abu Bakr.  Mawbakhti writes of a group that said they would not pay tax alms until it was known who was holding the government; therefore, they distributed the tax alms among the poor. 
Maqdisi, too, says, “A group of them refused to pay tax alms while others opposed rejected the principle of tax alms.” 
Besides not recognizing Abu Bakr's rule, another problem of the tribes was that after hearing the news of the Prophet's passing, they severed their relations with Medina. They only believed in having a religious connection with Medina, and when the Prophet of Islam passed away, they felt no need for accepting the rule of someone else. Therefore, since they refused to pay tax alms to Medina, they were labeled apostate. 
These tribes believed there was no need to assign a single ruler for all Muslims and that if they obeyed Muhammad, it was because he was a prophet. But, after his demise, there would be no need to obey others. They said:
ÃØÚäÜÇ ÑÓæá Çááå ãÇ ßÇä ÈíääÇ ÝíÜÜÜÇ áÚÈÇÏ Çááå ãÇ áÃÈí ÈßÑ
ÅÐÇ ãÇÊ ÈßÑ ÞÇã ÈßÑ ãßÇäÜå æÊáßã áÚãÑ Çááå ÞÇÕãÉ ÇáÙåÑ
We obeyed the Messenger when he was alive but why shall we obey Abu Bakr?
When Abu Bakr died, a man like him came to power, that is - by God - backbreaking. 
Thus, they did not deem it necessary to obey the rule of Medina and the rulers of Medina counted them among apostates. 
Muhammad Ibn Idris Shafi'i writes, “This was because Arabs living in the outskirts of Mecca knew no rule and resented being ruled by others. The reason they accepted to obey the Messenger of God, was because they did not consider anyone else deserving obedience.” 
This reasoning has been brought in the poetry of Malik Ibn Nuwayra. Addressing his tribe, he said:
æÞáÊ ÎÐæÇ ÃãæÇáßã ÛíÑ ÎÇÆÝ æáÇ äÇÙÜÑ ÝíãÇ íÌÆ ãä ÇáÛÏ
ÝÜÅä ÞÇã ÈÇáÃãÑ ÇáãÎæøÝ ÞÇÆã ãäÚäÇ æÞáäÇ: ÇáÏíä Ïíä ãÍãÏ
“I told you to take your money (tax alms) with no fear and no worries of what happens tomorrow, If someone assumes power, we will tell him, the only religion is the religion of Muhammad.” 
Abu Bakr's insistence on collecting tax alms from all tribes was to strengthen his government in Medina.
He said, “If they do not pay me the tax alms they used to pay to the Prophet (S) every year, I will fight them.” 
There is no doubt that the majority of the Prophet's companions did not like Abu Bakr's idea of war  but they obeyed him regardless because he was the ruler.
Maqdisi said the first dispute among Muslims was leadership while the second was fighting those who refused to pay tax alms. Muslims opposed Abu Bakr's view of tax alms collection but after a while, the majority of them accepted his rule. The opposition remained and some Muslims believed fighting them was a mistake. 
We quoted 'Umar as saying that 'Ali (a) might avoid fighting the Kinda people. Elsewhere, we said Abu Bakr was ready to fight them himself, but Imam 'Ali (a) asked him to stay in Medina  and send another one to fight them. Obviously, a group of those the caliph fought against were real apostates.
Another quotation from Mada'ini says after Imam 'Ali (a) opposed Abu Bakr, 'Uthman told Imam Ali, “Nobody will join the Muslim army to fight the apostates if you do not swear allegiance to Abu Bakr.” 'Uthman's insistence made Imam 'Ali swear allegiance to Abu Bakr. 
On the other hand, there were some people in Medina who wished for the success of apostates to once again maintain their infidel beliefs of the Dark Age. One day, a man of the Umayya and another man from the Ansar were boasting for each other.
The former said, “When the Prophet of Islam passed away, the majority of his companions were from the Umayya.”
The Ansari man replied, “Yes.” æ áßäåã ÍÇáÝæÇ Ãåá ÇáÑÏÉ Úáì åÏã ÇáÇÓáÇã  “They allied with the atheists to destroy Islam.”
'Ayisha, too, has said about wide-scale discord in Medina in the first days of his father's caliphate.  Also, Mecca was about to return to absolute apostasy after the Prophet's demise, but Suhayl Ibn 'Amr's remarks stabilized Mecca's situation.
Ibn Athir writes, “After the Prophet's passing, Mecca was on the verge of apostasy and 'Attab Ibn Asid sought a hiding.”
Suhayl Ibn 'Amr stood up and addressed the people of Mecca, áÇÊßæäæÇ ÂÎÑ ãä ÇÓáã æÃæá ãä ÇÑÊÏ
“Do not be the last one to embrace Islam and the first one to become an apostate.” 
At any rate, we must not ignore the fact that Medina's resistance against apostasy helped the administration in the city to be stronger and bring other lands under its control after passing through this tortuous period. Khalifa Ibn Khayyat has listed the apostates as follows,
Tulayha Ibn Khuwaylad, Banu Salim, Banu Tamim, Banu Yamama, Banu Bahrayn, Banu Umman, Banu Najir, Haďramawt and Banu Yemen, Banu Radda. 
Abu Bakr’s Agents
It is known to all that 'Umar was Abu Bakr's closest companion and friend. The Prophet of Islam had spelled their brotherhood union along with the Muhajirun. 
Although Abu Bakr was a major architect of the issue of caliphate and showed he was better than 'Umar in his battles against apostates, accepted 'Umar's views in many cases due to 'Umar's seriousness and toughness. These two were complementary to each other. We wrote that during the Saqifa developments, too, they were always together. It was due to this insistence that during the Saqifa issue, Imam 'Ali (a) accused 'Umar of trying to secure his own future. 
Abu Bakr said of 'Umar, “He is the dearest of people to me.” 
Ibn Abi l-Hadid says, “Abu Bakr could not gain (the) caliphate if 'Umar had not helped him.” 
It is said that Abu Bakr appointed 'Umar as a judge.  Also, he used to lead congregational prayers when Abu Bakr was absent. 
It was in the 11th Hijra year that Abu Bakr appointed him “emir of the pilgrims to Mecca”.  Khalifa Ibn Khayyat, listing Abu Bakr's emirs, writes, æÚáì ÃãÑå ßáå æÇáÞÖÇÁ ÚãÑ Èä ÇáÎØÇÈ “Every affair including judiciary one of 'Umar Ibn Khattab.” 
'Umar's influence on Abu Bakr was so immense that he dissuaded the caliph from appointing Khalid Ibn Sa'id as the commander of the Muslim army dispatched to Damascus and instead, sent Yazid Ibn Abi Sufyan. After returning to Medina and seeing Abu Bakr's choice, Khalid Ibn Sa'id refused to swear allegiance to the caliph for some time. 
'Umar, himself, was aware of his power so he made use of his rank and divided the properties of Mu'adh Ibn Jabal into two halves and took one half for Bayt al-Mal, the Treasury of Muslims.  He did the same thing later to the governors of cities when he assumed caliphate. Abu Bakr could not do anything in the absence of 'Umar, so when he wanted to send Usama's army to Damascus, he asked Usama, the commander of the army, to let 'Umar stay with the caliph and help him in the administration of affairs. 
Also, once when Khalid had made a mistake and Abu Bakr would not agree to write a letter of protest to him, 'Umar wrote a letter himself, but Khalid paid to attention to it and said he knew 'Umar had done it. 
At any rate, 'Umar's influence and the strong link between the two, made Abu Bakr appoint him as his successor. In other words, people did not consider their caliphate two separate things and from the very beginning, they saw one of them as successor to the other one. 
For the same reason, when Abu Bakr was in coma and wanted to write an agreement about his successor, his scribe, 'Uthman, wrote 'Umar's name in the agreement because he knew whom the caliph was thinking of.
Khalid Ibn Walid was another functionary of Abu Bakr. He belonged to the tribe of Banu Makhzum, a family of the Quraysh, who converted to Islam on Safar 1st, 8th AH.  He was physically a powerful man but void of ethical values. He committed various faults when the Prophet (S) was alive.
Some documents state it was the Prophet (S) who named him “God's sword” but Ibn Durayd and others say Abu Bakr gave him the title.  He got the title when he killed Malik Ibn Nuwayra unfairly and when people like 'Umar asked Abu Bakr to punish him. But the caliph said he was a sword hoisted by God and he would never bring it down.  According to Ibn A'tham, Khalid named himself “Sayf Allah or God's sword” and Abu Bakr approved it. 
It is said that Khalid was a supporter of Abu Bakr and an opponent of Imam 'Ali (a).  He also accompanied the group who invaded Imam 'Ali's house to force him into swearing allegiance with Abu Bakr.  He is widely believed to be a person who prepared the ground for Abu Bakr's caliphate. 
The story of Malik Ibn Nuwayra's murder, and the subsequent rape of his wife which Ibn A'tham said he did upon the consensus of people of knowledge displays the weak moral character of Khalid. However, Abu Bakr insisted on keeping him the commander of his army and sending him to crack down on apostates and false prophets.
Abu Bakr defended Khalid with the justification that Khalid had acted on Ijtihad and so he did not deserve punishment. One day Khalid burnt some of the captives of apostates with fire. When 'Umar objected, Abu Bakr said he was God's sword. 
'Umar's objection was why he had appointed a commander who killed people and tortured them with fire.  Apparently, despite all his attention to 'Umar, the caliph was unwilling to stop backing Khalid, and still, it is interesting to know that when 'Umar, himself, took power as the second caliph, unlike his earlier emphasis on stoning Khalid for raping Malik Ibn Nuwayra's wife, he sufficed to sacking him. 
Khalid was sure his acts would meet no objection on the part of Abu Bakr and if he received a letter of punishment from the caliph, it was from 'Umar; otherwise, Abu Bakr trusted him.  Sometimes, he committed self-authorized acts because he was sure of Abu Bakr's support. 
Abu Bakr once said, “No mother can give birth to someone like Khalid.”  Once when he killed two people who had letters of clemency from Abu Bakr, some people complained about it, but Abu Bakr defended Khalid as usual.  When 'Umar sat on the throne as the second caliphate, he immediately fired Khalid from the command of Damascus's army and replaced him with Abu 'Ubayda Jarrah.
He said, “I sacked Khalid to show that God helps His religion.” 
When Khalid was busy fighting in Iraq and received his letter of abdication to Damascus, he said, ”'Umar's jealousy did not allow me to achieve the conquest of Iraq.” 
According to Anas Ibn Malik, 'Umar used to tell Abu Bakr, “Write to Khalid to ask for your permission before doing anything.”
Abu Bakr wrote but Khalid responded, “You must leave me free in whatever I do; otherwise, I will resign.”
'Umar said, “Dismiss him”, but the caliph did not accept.  Khalid died in Medina or Damascus ) in the 21st AH and accidentally, he appointed 'Umar as guardian of his will. Ibn Sa'd quoted 'Umar as saying, “We had ill thoughts about Khalid, but we were wrong.” 
'Umar opposed crying over the dead and said he had heard from the Prophet (S) that, Åä ÇáãíÊ áíÚÐÈ ÈÈßÇÁ Çåáå “The dead person suffers when his family cries for him.”
However, he allowed the women of Banu Makhzum to cry for Khalid.  More surprising, 'Umar said at the time of his death, “If Khalid Ibn Walid were alive, I would appoint him as my successor.” 
Abu 'Ubayda Jarrah was another pillar of power for Abu Bakr's caliphate. He, along with 'Umar and Abu Bakr were present in Saqifa Banu Sa'ida. He had an oath of brotherhood with Salim Mawla Hudhayfa  who was also influential in the issue of caliphate.
'Umar said about him, “If Salim were alive, I would make him my successor.” 
It should be noted that 'Umar said the same thing about Abu 'Ubayda at the time of his death.  Abu 'Ubayda was first appointed in charge of the Treasury of Muslims but later, became the commander of the Damascus army16 and served until his death in 18th Hijra year when he died in Amawas plague.
The commanders and functionaries of Abu Bakr were Yazid Ibn Abi Sufyan, 'Amr Ibn 'As, Shurahbil Ibn Hasana (18 H)  and 'Akrama Ibn Abi Jahl. Among his appointees, there were some people serving since the Prophet's time. Mu'adh Ibn Jabal in Yemen, 'Attab Ibn Asid in Mecca and 'Ala' Ibn Haďrami in Bahrayn were some of these people.
According to some documents, Abu Bakr appointed Anas as the ruler of Bahrayn. Perhaps, it was another part of Bahrayn. Muhajir Ibn Abi Umayya ruled in San'a, Ziyad Ibn Lubayd in the coastal regions of Yemen, Ya'la Ibn Umayya in Khawlan, 'Uthman Ibn Abi l-'As in Ta'if, and Sulayt Ibn Qays ruled in Yamama. Also, it is said that 'Uthman was Abu Bakr's scribe. 
It is evident that the list does not include important figures of the Prophet's companions, especially from the Ansar. Apparently, this can be suitable evidence on the caliphate's neglect of the Ansar.
Conquest of Damascus
The greater Syria was a land bounded by the Mediterranean Sea, the Western banks of the Euphrates, the northern border of Hijaz, the southern border of the ancient Eastern Rome and modern-day Turkey. Presently, this land includes the countries of Syria, Jordan, Lebanon and Palestine. The new border demarcation was made during the developments following World War I.
The name of Syria has always existed since ancient times and Herodot (425 AD) has called this land Syria. Probably, the name Syria has been taken from the word ”'Ashuriyya” attributed to Assyrians, although some have rejected this notion. 
Before falling to Muslims, the region of greater Syria was a colony of the Eastern Roman Empire. Centuries before the advent of Islam, big tribes of Arabs migrated from Hijaz - mostly from south- to this land. The most important tribes recorded in the early advent of Islam, were, Quďa'a, Salih, Ghasasina, Judham, Lakhm, Kalb, Tanukh, and Bahra'. These tribes were sparse and scattered in the developed land of ancient Syria and each settled in a city or village.
These tribes forgot their Arab rites and rituals due to the many years of life with the Romans and the vast majority of them converted to Christianity.
However, they had retained parts of their Arab nature. The first sign of their conversion to Christianity was mixing their Arab language with Syriac, and basically, Syriac had become their scientific language. Therefore, it was recommended later that Arabic should not be taught from Qaďa'a and Ghassan because they read books in Syriac and naturally, their language had become mixed. 
Shaykhu insists in showing that all Arabs living in the greater Syria had converted to Christianity before the advent of Islam. We believe this is an overstatement. Earlier, we negated his views on the Christianity of the tribes of Aws and Khazraj. At any rate - true of false - he has provided a list of Arab tribes who converted to Christianity. 
Years before the advent of Islam, the Arabs of this land were allies of Romans in their battle against Iranians and fought the Iranian army and its allied Arabs from Iraq. In those years, the Roman army consisted of Arabs and Romans.
Damascus Arabs held different views from Arabs living on Hijaz and they had different social behavior as well. The Arabs of Damascus had left their Bedouin life because they lived in a developed area and had become city dwellers in Damascus, Halab (Aleppo), Hims, etc. Their commonalities with the Romans made some of them migrate to Rome after the advent of Islam. 
Of course, Romans always feared that racial commonality would urge the Arab tribes of Damascus to accept Islam. A more serious problem was difference in religion between the Christians of Damascus and the church of Constantinople in a way that they were greatly persecuted by the Eastern Church.
The Christians of Damascus believed in the Ya'qubi sect  and it was a heretical practice in view of the Eastern Church.
They believed that Damascus Christianity was excellent in innovation!  The religious difference of Damascus's Arab Christians with the Eastern Roman Church, to many, was one of the reasons for the consecutive Islamic conquests in the greater Syria. 
In addition to the Arab residents of the greater Syria, numerous Nibtiyan, too, who were descendants of the earlier tribes and rulers in the region, lived in that land. Also, many Jews who are said to be between 100 to 200 thousands lived in that land. 
We mentioned earlier that at the time of the advent of Islam, the greater Syria was under the domination of the Eastern Roman empire. However, since centuries ago, local rulers had the power in that land. The Nibtiyan government ruled first, followed by the Tadmur government and finally, the government of Ghassanid who were from the tribe of Ghasasina. These came from Yemen apparently after the destruction of the Ma'rab Dam.
This tribe converted to Christianity in the 4th century AD. Jafna Ibn 'Amr, from the elders of the tribe, was the founder of the Ghassani dynasty and there are ambiguous quotations that between 11 to 32 rulers of this dynasty ruled in Damascus. There is little we know about a limited number of these more recent rulers. Harith Ibn Jabala was one of their renowned personalities who ruled between the years 529-569.
He fought the Lakhmids -the Arab rivals of the Ghasasina who ruled Iraq - and helped his tribe rise to fame. He won the title of “Philark” meaning chieftain and also Bitriq (Patrick) from the Roman emperor for his services. The Ya'qubiyya sect spread in Damascus in his time. After Harith, his son, Mundhir, replaced him and ruled until 581, when crisis engulfed Damascus. 
Between the years 611 and 614, Iranians fiercely invaded these regions and captured Jerusalem. Later, (Hiraql) Heraclitus could regain Jerusalem from Iranians. The names of Ghassani princes ruling some cities and their command of the battle between the Roman-Arab army and the army of Islam indicates that the Ghasasinah still had great influence in Damascus and Constantinople.
Jabala Ibn 'Ayham Ghassani, a commander of the Roman army at Yarmuk, was one of these influential princes who converted to Islam but became an apostate and went to the Roman emperor for certain reasons mentioned elsewhere.
Heraclitus was the son of Herakleios, whose father ruled in Christian Africa on behalf of the Roman Empire. The Eastern Empire Roman Empire experienced serious crises in the closing years of the sixth century AD and the early years of the 7th century.
The attacks of Awars and Islaws from the West caused problems for this vast land, but most pressing were the civil wars. A sergeant named Fukas united people and revolted against the government of the aristocrats and killed Emperor Mavrikius and all his children. This civil unrest prompted Khusraw Parviz to invade the greater Syria and capture Jerusalem in 614. He continued his assaults on Asia Minor.
The aristocrats of Constantinople sought help from Heraclitos, the ruler of Africa. He sent his son, who was also named Heraclitos, to Rome. The son who was a brave man, succeeded in defeating Fukas and put on the crown of emperor. The capture of Jerusalem was a good pretext for inciting Christians to fight Iranians. After restoring calm, Heraclitos set off to fight Iranians in the year 622 and after six years of sustaining consecutive defeats, he finally managed to pursue Iranians as far as the gate of Ctesiphon and made them accept peace.  These incidents took place in the 7th and 8th years of Hijra.
When Heraclitos was busy reorganizing his affairs, Muslims made their first attacks on Damascus and captured the city after a while. The last days of the empire coincided with the conquest of Egypt in 640 AD. 
The greater Syria was the first priority for Muslims because they had managed to make the Quraysh sign the Hudaybiyya peace accord after years and get ready for spreading Islam outside Hijaz.
The Prophet of Islam sent a few messengers to these regions. Harith Ibn 'Umayr was one of these messengers who took a letter to the ruler of Basra. He was killed by Shurahbil Ibn 'Amr of the Ghassani dynasty. Then, the Prophet of Islam sent his 3,000-strong army under the command of Ja’far Ibn Abi Talib, Zayd Ibn Haritha and 'Abd Allah Ibn-Rawaha to Muta in southern Damascus.
The army prepared to fight Muslims in Damascus- according to Ibn Ishaq - was a combination of the Roman army and the Arab tribes of Lakhm, Judham, Balqi, Buhra´, and Bali.  Muslims were unsuccessful and after the martyrdom of their commanders and a number of others, they could only return to Medina. The Tabuk operations were the Prophet's next measure.
This operation, likewise, entailed nothing for Muslims except several accords with some Arab tribes. The Prophet mobilized another army in the final days of his life under Usama Ibn Zayd but it was sent to Damascus after his death and returned home empty-handed. All these army deployments show the importance of Damascus in view of the Prophet.
Damascus was close to Medina and Muslims were quite familiar with its importance. It came out in the following years that Damascus was more important than Iraq to the succeeding caliphs.
With the end of the Radda operations, Abu Bakr wrote letters to the people of Mecca, Ta'if, Yemen and all Arabs in Hijaz and Najd and summoned them for Jihad or holy war.
In his letters, he promised the booties in Rome. Numerous people rushed to Medina from tribes across Hijaz.  A strong army of Muslims left for Damascus in the 12th AH (633 AD). Abu Bakr divided the army of Islam into three armies with three commanders. The first army commanded by 'Amr Ibn 'As, was to leave for 'Ayla in the Gulf of 'Uqba. The second army's commander was Yazid Ibn Abi Sufyan and the third commander was Shurahbil Ibn Hasana.
These two commanders were sent to a region between Tabuk and Mu'an. Khalid Ibn Sa'id was supposed to command one of these armies, but due to his objection to Abu Bakr's caliphate, upon 'Umar's emphasis, they replaced him with Yazid Ibn Abi Sufyan.  A short while later, Abu 'Ubayda Jarrah joined them with his auxiliary men and he commanded all forces when they all operated in the same region. Some people believe he commanded an army from the beginning.
The first clashes of Muslims with Romans occurred in a region called “Wadi al-'Araba”, south of the Dead Sea. Palestinian governor, Sergius, was the commander of the Roman army. He was killed in this war and his army was defeated. The Muslims advanced along the Mediterranean coasts  and each of the armies fought in a region and joined others wherever necessary.  In the beginning, the Muslim armies had 3000 men each, but Abu Bakr sent fresh forces and the number of Muslim fighters in each army rose to 7500.
Shortly after, the total number of the army of Islam increased to 24000 men. 
After the 'Araba battle, the second encounter was made in a village of district of Ghazza called Dathin. This battle which took place in the month of Muharram of the 13th year of Hijra,  ended in Muslims' victory.
Baladhuri has written about the war of Dathin first and then, about the 'Araba battle, but he has mentioned a narration saying the battle of Dathin happened in the beginning. According to historians, the Muslim army did not face any obstacles which required them to use their weapons on their way from Hijaz to Wadi 'Araba. These sweeping victories frightened Heraclitos and made him recruit forces. The news of the Roman army's recruitment reached Medina and the caliph ordered stopping the operations temporarily on the Iraqi border.
He sent Khalid Ibn Walid and his army to Damascus. The Muslims captured Basra and Ma'ab after Dathin in Rabi' al-Awwal of the 13th Hijra year. Then, they moved towards Damascus. Hearing the news of the enemy's concentration in Ujnadayn, Muslims moved towards that place first. This bloody battle ended in the victory of Muslims in the Jumadi al-Awwal or Jumadi al-Thani of the 13th Hijra year although many Muslims, too, were martyred. 
It was after this defeat of the Romans that Heraclitos who was in Hims, left for Antioch. While Muslims were on their way to Damascus, the enemy regrouped and encountered the army of Islam in Marj as-Safar. This war took place in the month of Muharram of the 14th Hijra year and once again, Muslims defeated the enemy. After that, Damascus was totally besieged by the army of Islam.
It is said that while Abu 'Ubayda had managed to open his way into the city, the archbishop of the city signed a peace accord with Khalid Ibn Walid on the other hand and Abu 'Ubayda, too, had to accept it despite Muslims' objection.
The conquest of Damascus forced many residents of the city who were mostly Roman or Arabs affiliated to them, into leaving for Antioch and joining Heraclitos. After their departure, Muslims settled in their unsettled houses.  Damascus fell to Muslims in Rajab of 14th Hijra year, but Abu Bakr had died in Jumadi al-Thani of the 13th Hijra year after two years and three months and a few days of caliphate.