The Communist Party has announced some high-profile expulsions in the same week as its 93rd anniversary - a reminder that President Xi Jinping sees the fight against corruption at every level as crucial to maintaining its rule. One case in particular set them apart - that of Xu Caihou, who recently retired as a vice-chairman of the Central Military Commission and a member of the Politburo. Xu is the highest-ranking PLA officer ever to face prosecution for corruption. Military and political rank alone do not convey the full significance of his downfall. On his watch corruption flourished at the most senior levels of the PLA. It coincided with the term of office of President Hu Jintao, also CMC chairman, who was not known for exercising strong control over the armed forces. Xu was therefore effectively in charge of day-to-day management for a decade, during which it was common for senior officers to seek bribes in return for promotions. As a result he must have counted a lot of allies among them. For Xi to have brought him down is therefore no small feat and will have taken some political courage. It is testament to his efforts, as current CMC chairman as well as party leader, to assert his authority over the PLA and consolidate his power. At the same time he is pursuing his anti-corruption campaign in civilian ranks. The party this week also announced the expulsion of six former officials who were close aides or allies of former domestic security tsar Zhou Yongkang , the first present or former Politburo Standing Committee member to face investigation for corruption. This has naturally led to speculation that news of Zhou's fate may be imminent. It has also prompted discussion of where Xi's campaign will end, given the widespread perception that so many officials are corrupt. It seems that graft is seen as so extensive that, for now, the symptoms should be tackled and contained in order to buy more time to tackle the root causes. The latter will call for political and economic reforms to make government more accountable, transparent and publicly supervised. Meanwhile, officials exposed by corruption whistle-blowers or caught in the cross hairs of the anti-graft campaign cannot expect mercy or protection, regardless of their factional or ideological allegiance. This could serve the purpose of removing political obstacles to reforms endorsed by the party's third plenum last year, including a bigger role for market forces in the pursuit of sustainable economic growth.