The Bulgars under Boris I were persuaded by Moravian Prince Rastislav to attack Louis the German of East Francia. The Bulgar-Slav campaign ended in disaster, and a peace was signed in 855. The following year, the Byzantine army, led by Michael III and "caesar" Bardas, recaptured Philippopolis (Plovdiv), the region of Zagora and the ports around the Gulf of Burgas on the Black Sea. In 863, the Byzantines invaded the Khanate once again, during a period of famine and natural disasters. Boris I was forced to sign a peace and to convert to Christianity, in return for which he was gifted Zagora. The cradle of the Bulgarian Orthodox Church was founded about 870 in Pliska.