This is a repeat of questions 92 and 168. Hazrat Abu Bakr's (RA) caliphate lasted approximately 2 years and 3 months (11-13 AH / 632-634 CE). Despite the brief duration, his achievements were monumental: he maintained Muslim unity after the Prophet's death, fought and won the Ridda Wars against apostasy and false prophets, initiated the compilation of the Quran, and began the expansion of Islam into Syria and Iraq. He died at age 63 from natural causes.