With the death of Muhammad, the Muslim community was faced with the problem of succession.  Who would be its leader?  There were four persons obviously marked for leadership: Abu Bakr al-Siddeeq, who had not only accompanied Muhammad to Medina ten years before, but had been appointed to take the place of the Prophet as leader of public prayer during Muhammad’s last illness; Umar ibn al-Khattab, an able and trusted Companion of the Prophet; Uthman ibn ‘Affan, a respected early convert; and ‘Ali ibn Abi Talib, Muhammad’s cousin and son-in-law.  Their piousness and ability to govern the affairs of the Islamic nation was uniformly par excellence.  At a meeting held to decide the new leadership, Umar grasped Abu Bakr’s hand and gave his allegiance to him, the traditional sign of recognition of a new leader.  By dusk, everyone concurred, and Abu Bakr had been recognized as the khaleefah of Muhammad.  Khaleefah - anglicized as caliph - is a word meaning “successor”, but also suggesting what his historical role would be: to govern according to the Quran and the practice of the Prophet.

Abu Bakr’s caliphate was short, but important.  An exemplary leader, he lived simply, assiduously fulfilled his religious obligations, and was accessible and sympathetic to his people.  But he also stood firm when some tribes, who had only nominally accepted Islam, renounced it in the wake of the Prophet’s death.  In what was a major accomplishment, Abu Bakr swiftly disciplined them.  Later, he consolidated the support of the tribes within the Arabian Peninsula and subsequently funneled their energies against the powerful empires of the East: the Sassanians in Persia and the Byzantines in Syria, Palestine, and Egypt.  In short, he demonstrated the viability of the Muslim state.

The second caliph, Umar - appointed by Abu Bakr - continued to demonstrate that viability.  Adopting the title Ameer al-Mumineen, or Commander of the Believers, Umar extended Islam’s temporal rule over Syria, Egypt, Iraq, and Persia in what, from a purely military standpoint, were astonishing victories.  Within four years after the death of the Prophet, the Muslim state had extended its sway over all of Syria and had, at a famous battle fought during a sandstorm near the River Yarmuk, blunted the power of the Byzantines - whose ruler, Heraclius, had shortly before refused the call to accept Islam.

Even more astonishingly, the Muslim state administered the conquered territories with a tolerance almost unheard of in that age.  At Damascus, for example, the Muslim leader, Khalid ibn al-Walid, signed a treaty which read as follows:

This is what Khalid ibn al-Walid would grant to the inhabitants of Damascus if he enters therein: he promises to give them security for their lives, property and churches.  Their city wall shall not be demolished; neither shall any Muslim be quartered in their houses.  Thereunto we give them the pact of God and the protection of His Prophet, the caliphs and the believers.  So long as they pay the poll tax, nothing but good shall befall them.

This tolerance was typical of Islam.  A year after Yarmook, Umar, in the military camp of al-Jabiyah on the Golan Heights, received word that the Byzantines were ready to surrender Jerusalem.  Consequently,  he rode there to accept the surrender in person.  According to one account, he entered the city alone and clad in a simple cloak, astounding a populace accustomed to the sumptuous garb and court ceremonials of the Byzantines and Persians.  He astounded them still further when he set their fears at rest by negotiating a generous treaty in which he told them: “In the name of God ...  you have complete security for your churches, which shall not be occupied by the Muslims or destroyed.”

This policy was to prove successful everywhere.  In Syria, for example, many Christians who had been involved in bitter theological disputes with Byzantine authorities - and persecuted for it - welcomed the coming of Islam as an end to tyranny.  And in Egypt, which Amr ibn al-As took from the Byzantines after a daring march across the Sinai Peninsula, the Coptic Christians not only welcomed the Arabs, but enthusiastically assisted them.

This pattern was repeated throughout the Byzantine Empire.  Conflict among Greek Orthodox, Syrian Monophysites, Copts, and Nestorian Christians contributed to the failure of the Byzantines - always regarded as intruders - to develop popular support, while the tolerance which Muslims showed toward Christians and Jews removed the primary cause for opposing them.

Umar adopted this attitude in administrative matters as well.  Although he assigned Muslim governors to the new provinces, existing Byzantine and Persian administrations were retained wherever possible.  For fifty years, in fact, Greek remained the chancery language of Syria, Egypt, and Palestine, while Pahlavi, the chancery language of the Sassanians, continued to be used in Mesopotamia and Persia.

Umar, who served as caliph for ten years, ended his rule with a significant victory over the Persian Empire.  The struggle with the Sassanid realm had opened in 636 at al-Qadisiyah, near Ctesiphon in Iraq, where Muslim cavalry had successfully coped with elephants used by the Persians as a kind of primitive tank.  Now with the Battle of Nihavand, called the “Conquest of Conquests,” Umar sealed the fate of Persia; henceforth it was to be one of the most important provinces in the Muslim Empire.

His caliphate was a high point in early Islamic history.  He was noted for his justice, social ideals, administration, and statesmanship.  His innovations left an all enduring imprint on social welfare, taxation, and the financial and administrative fabric of the growing empire.