On the Prophet's death in 632 the community faced its first succession crisis. At the gathering known as the Saqifa, Abu Bakr was acknowledged as khalifa, successor or caliph, the beginning of the institution that would govern much of the Muslim world for centuries. His reign lasted only about two years, but two developments are ascribed to it.
The first was the Ridda wars, the campaigns against Arabian tribes who, after Muhammad's death, withheld the alms-tax or followed rival prophets and so, in the caliphate's view, broke from the community. Abu Bakr's insistence on holding the tribes together, by force where necessary, is credited in the tradition with preserving the nascent state and clearing the way for the great conquests under his successors.
The second is the beginning of the collection of the Qur'an. A widely reported tradition holds that the death of many who had memorized the revelation in the battle of Yamama prompted Abu Bakr, urged by Umar, to have the scattered texts gathered, a first step in the process that the caliph Uthman would later complete. The historicity of the details is debated by modern scholars, but the tradition assigns to Abu Bakr the crucial initiative of preservation.