As crown prince, Xiao Gang was a distinguished poet, as well as patron of the poet Xu Li (徐攡). One of the crown prince's poems describes a languid life of lolling on an
ivory inlaid bed, surrounded by
feather curtains, with a
male prostitute. Given the poetry he wrote, some have asserted that Xiao Gang was
bisexual, but there is no direct evidence indicating such. Xu's style became known as "palace style," and initially, Emperor Wu was displeased about this development, but once Emperor Wu met Xu, he was impressed by Xu's talents, and became a patron of Xu himself as well. It is unclear whether Xiao Gang carried out much decision-making duties in the imperial administration, as Xiao Tong did before his death.
As Emperor Wu aged, Xiao Gang's younger brothers Xiao Xu (蕭續) the Prince of Luling, Xiao Guan (蕭綸) the Prince of Shaoling,
Xiao Yi the Prince of Xiangdong, and
Xiao Ji the Prince of Wuling grew less obedient of his edicts, and effectively exercised imperial powers in their provincial domains. Fearing that his brothers would seize power, Xiao Gang selected elite troops to be the palace guards for the crown prince's palace. He honored
Taoist philosophies, and often lectured on the
Tao Te Ching and the
Zhuangzi.
In
547, the
Eastern Wei general
Hou Jing, in a conflict with the new regent
Gao Cheng, surrendered the 13 provinces (the region between the
Yellow River and the
Huai River) to Liang, seeking aid from Liang. However, both Xiao Gang's cousin
Xiao Yuanming the Marquess of Zhenyang, and Hou himself, were defeated by the Eastern Wei general Murong Shaozong (慕容紹宗). Xiao Yuanming was captured, while Hou fled and, surprising the Liang governor of Southern Yu Province (南豫州, modern central
Anhui), Wei An (韋黯), seized the key city Shouyang (壽陽, in modern
Lu'an, Anhui, the capital of Southern Yu Province. Instead of punishing Hou, however, Emperor Wu allowed him to serve as the governor of Southern Yu Province. It is unclear whether Xiao Gang was involved in making these decisions, but he was clearly informed about them, as he revealed these decisions to his assistant He Jingrong (何敬容).
Soon, however, Hou, believing that Emperor Wu, who engaged in peace talks with Eastern Wei and appeared to be willing to betray him to exchange for Xiao Yuanming, rebelled in summer
548. Hou's army quickly advanced on Jiankang, assisted by Xiao Gang's cousin
Xiao Zhengde the Prince of Linhe, putting Jiankang under siege. Emperor Wu put Xiao Gang in charge of the defenses, but Xiao Gang was unsuccessful in preventing the outer city from falling. The imperial troops were forced to withdraw into the palace. When Hou then claimed that it was the corrupt official
Zhu Yi that he wanted to kill, Xiao Gang confirmed that Zhu was indeed corrupt, but advised against executing Zhu in that it would serve nothing in the campaign against Hou. Soon, Hou declared Xiao Zhengde emperor. While provincial troops gathered near Jiankang to try to relieve the besieged palace, those troops, commanded by Liu Zhongli (柳仲禮) and Xiao Guan, were unsuccessful, and ultimately, after Liu was nearly killed in a battle, Liu refused to engage Hou any further, leaving the palace troops to fend for themselves. (Xiao Yi and Xiao Ji, although they each had large numbers of troops in their domains, largely stood and sent only token troops.) In winter 548, Hou's general Fan Taobang (范桃棒) offered to rebel against Hou, and while Emperor Wu was initially in favor of the idea, Xiao Gang spoke against it, and it was not carried out. Soon, Fan was killed by Hou, and an opportunity was lost.
In spring
549, Xiao Gang tried to negotiate peace with Hou, whose troops had by then tired. Hou initially agreed -- with the terms being that he would be given the provinces west of the
Yangtze River. However, Hou soon reneged on the peace agreement and resumed the siege of the palace. Soon, the palace fell, and Emperor Wu and Xiao Gang were effectively taken as hostages, although Hou continued to formally honor them as emperor and crown prince, despite his earlier agreement with Xiao Zhengde to have them killed. (Hou soon deposed Xiao Zhengde and killed him.) Xiao Gang's attendants all fled, except for Xu Li and Yin Buhai (殷不害). The provincial troops which had come to Jiankang's aid were disbanded, and Hou was now in control of the capital region.
Meanwhile, Emperor Wu, while he was under Hou's control, was unwilling to yield, and he refused to carry out some of the acts that Hou wanted him to. Xiao Gang tried to urge Emperor Wu to follow Hou's requests, but Emperor Wu refused. Hou put Emperor Wu under closer guard, and Emperor Wu, in anger, soon grew ill and died. (Some historians believe that Hou starved Emperor Wu to death.) Xiao Gang did not dare to weep for Emperor Wu's death, and Hou made him emperor to succeed Emperor Wu (as Emperor Jianwen).