THERE had been rumours of his downfall since last year. On July 30th, they got him: Guo Boxiong, former vice-chairman of the Central Military Commission, which runs China’s armed forces, was expelled from the Communist Party for taking bribes. He is the most senior ranking official in the People's Liberation Army (PLA) to be toppled for corruption.

The move is a sign that President Xi Jinping’s campaign against corruption is still running at full tilt. Mr Guo’s son, also a senior officer, was put under investigation in March. But after Zhou Yongkang, China’s former security chief, was sentenced to life imprisonment in June for graft and leaking state secrets, some China-watchers suggested that Mr Xi might now scale back his efforts. The latest expulsion proves that view wrong. “One demon killed, all demons deterred,” ran a line in an article about Mr Guo in People’s Daily, a government mouthpiece.

The arrest is a further assertion of Mr Xi’s control over the military; he has stressed the “absolute leadership” of the party over the PLA since taking office in 2012. More than 15 senior ranking figures have been accused of corruption in the past year, including Xu Caihou, another high-ranking figure who died of bladder cancer earlier this year before his case could come to trial. As with the anti-corruption in other parts of the government, lesser ranking army officers have been netted along side the big names.

This is not just about control, however. Though Mr Xi needs the PLA’s support, he is also keen to modernise the army to make it a lean, fighting force readily able to deploy. Taking bribes for promotions, as Mr Guo is accused of, does not fit that goal. The PLA is a key tool by which Mr Xi hopes to project China’s power abroad: on September 3rd there will be a giant military parade in Beijing to mark the 70th anniversary of the second world war, which the government hopes that dignitaries from around the world will attend.

Mr Guo was put under investigation in April, according to the official announcement, but the news of his expulsion was broadcast only days ahead of “Army Day” on August 1st, which marks the 88th anniversary of the founding of the PLA. Not so much a morale-raising birthday present as an open warning to his peers.