In 548, the general Hou Jing, who had defected from Eastern Wei in 547, rebelled from his headquarters at Shouyang (壽陽, in modern Lu'an, Anhui). He quickly arrived at the capital Jiankang and, after capturing the outer city, put the palace under siege. Despite the desperate situation that the capital was in, Xiao Yi only sent partial troops, commanded by his heir apparent Xiao Fangdeng () and general Wang Sengbian, to join the other provincial troops to try to lift Jiankang's siege. However, the provincial troops, once they gathered, were hesitant to engage Hou's troops. Xiao Yi himself, commanding the majority of his troops, halted at the border between Jing Province and Ying Province (郢州, modern eastern Hubei), claiming that he needed to wait for the other provincial troops to gather before he could proceed. Meanwhile, as soon as he heard news that Emperor Wu had entered into peace with Hou in spring 549, he withdrew his troops entirely. Hou soon reneged on the peace agreement, however, and put the palace under siege again in earnest, and he soon captured it, seizing Emperor Wu and the crown prince Xiao Gang (Xiao Yi's older brother) effectively as hostages. The provincial troops already at Jiankang took no action and disbanded. Xiao Fangdeng and Wang Sengbian took their troops back to Jing Province. Upon their arrival, Xiao Yi's response was to strengthen the defense of his headquarters at Jiangling. He declined requests by several other provincial governors that he formally undertake imperial powers, but then began to act in accordance therewith, including commissioning generals and governors and creating titles, particularly after his cousin Xiao Shao () the Marquess of Shangjia fled out of Jiankang and claimed to carry a secret edict from Emperor Wu authorizing Xiao Yi to exercise those authorities. When Emperor Wu died in summer 549 and was succeeded by Xiao Gang (as Emperor Jianwen), Xiao Yi learned the news of Emperor Wu's death but kept it secret from his people and army.