The reign of Abu Bakr lasted a little over two years, and he kept Omar close in order to prepare him for the role of caliph. But the leadership of the community Omar inherited came with the burden of waging two simultaneous wars against empires that had bordered the Arabs for as long as they they could remember. We very briefly discussed the Byzantine and Sassanid empires in the previous episode, and today we'll talk about the challenges they posed to the new caliph, and how he responded to them and other dangers to the Umma.