After Guo's retirement, Xi Jinping, the General Secretary of the Communist Party of China and supreme commander of the PLA, began a far-reaching anti-corruption campaign. Guo was subject of intense rumours surrounding possible involvement with corruption during his time in office, particularly in overseas Chinese media. Guo and his former colleague of the same rank, retired general Xu Caihou, attended a new year's gala in early 2014, signalling that both may have "weathered the storm". However, shortly thereafter, in the summer of 2014, as part of the fallout of the Gu Junshan case, Xu was court-martialed and expelled from the party. After Xu's fall, Guo was euphemistically referred to in Chinese-language media as the "Northwest Wolf", an oblique reference to Xi Jinping's slogan to "crack down on 'tigers' and 'flies'." Sensing impending doom, friends from Guo's hometown visited Guo in Beijing, urging him to "clarify the situation to the authorities" to avoid the same fate as Xu. In response, Guo reportedly said, "some things cannot be easily clarified." His fate was sealed. In February 2015, Guo's son, Guo Zhenggang, a rear admiral in the PLA Navy, and his wife, were detained for investigation by military authorities in connection to business and real estate dealings. This was followed by reports in international media that Guo himself was also undergoing investigation. On March 5, in response to a reporter's question about whether Guo Boxiong was under investigation, the party's main anti-corruption crusader in the military, General Liu Yuan, responded simply with the phrase "ni dongde" After approval from the Politburo of the Communist Party of China, Guo was placed under investigation on April 9, 2015 by the Commission for Discipline Inspection of the Central Military Commission. On July 30, following another Politburo meeting, the Central Commission for Discipline Inspection, the party's top anti-corruption body, released a statement charging Guo with taking bribes personally and through his family in exchange "for aiding in the promotion ." He was duly expelled from the Communist Party of China and his case moved to military prosecution authorities for further processing. Guo was, remarkably, the fourth member of the 17th Politburo of the Communist Party of China to be expelled from the Communist Party. On July 25, 2016, Guo was sentenced to life imprisonment for bribery.
Personal life
Guo Boxiong has a brother, Guo Boquan born in 1961, who, until 2015, headed up the Department of Civil Affairs of Shaanxi province and a former official in the city of Weinan. Boquan was reportedly detained by the authorities for investigation in March 2015, though it seemed that he was able to maintain his position following Guo Boxiong's investigation. Guo Boxiong has a son, Guo Zhenggang, who was a major general in the People's Liberation Army, who held a leading military post in Zhejiang province; Zhenggang was also detained for investigation in February 2015.