Whether by accident or design, Jiang overheard at least part of Guo’s address, according to two sources.

“I was told that Jiang happened to eavesdrop on Guo’s speech to military officers saying he had pledged loyalty to the then new ‘core leadership of Jiang’. As a result, Jiang was very happy,” said a source close to the PLA’s Academy of Military Science. Not long afterwards, Guo was made head of the Lanzhou military command.

By the time he retired in 2012, Guo had risen to the highest ranks of the military.

As deputy chairman of the Central Military Command (CMC), he was in a position that allowed him to decide how the defence budget was spent and which companies received contracts. In 2012, the sum amounted to 670 billion yuan (HK$835 billion).

He now faces prosecution for abusing his position to take bribes, the latest senior official to be targeted in the government's massive anti-corruption campaign.

The investigation into Guo is expected to have much bigger ramifications than the corruption probe into another former senior military leader, the late Xu Caihou, according to a Shanghai-based retired senior colonel, who requested anonymity. Xu, who was promoted to a CMC deputy chairman during Jiang’s rule but two years after Guo, effectively served as the junior partner of the two. Xu died in March from bladder cancer.

“Guo’s case is more serious than Xu Caihou’s because everyone promoted by Xu should have got approval from Guo first. He shared certain bribe-taking by Xu,” he said.

“Indeed, Guo had taken charge of military training and weaponry during his 10-year-long CMC vice-chairmanship, which gave him opportunities to embezzle training budgets and take kickbacks for arms purchases,” the retired senior colonel said.

It was not possible to contact Guo to respond to the allegations made against him, but the scale of his alleged corruption was suggested at a forum organised in Beijing by the Hong Kong-based Phoenix Television’s Ifeng.com in September last year.

Zhang Musheng, an adviser to General Liu Yuan, the political commissar of the PLA General Logistics Department who is leading the anti-graft campaign in the army, said: “Xu Caihou alone took at least 1 billion yuan [of bribes], but there is another one worse than him. That person was not only involved in buying and selling ranks, but also found to [have] embezzled military spending,” Zhang said.

According to a Beijing-based retired senior colonel, Guo was the central figure in the “Northwest faction”, which was separate but intertwined with a group that Xu controlled before he was taken from his bed at the 301 Military Hospital in Beijing and placed under investigation in March of last year.

President Xi Jinping and state media have in recent months stressed that factions pose a serious threat to the Communist Party and would not be tolerated. The criticisms were a departure from the party’s preferred narrative, which is that cadres are united.

“Both Xu and Guo had formed their own factions, but Xu was brought down first because he had intentionally arranged his men to occupy CMC posts before Xi formally succeeded Hu Jintao as chairman in late 2012. That definitely made Xi very angry,” the senior colonel said.

The power clusters within the military are not easily compared to other factions state media have identified – the petroleum, Shanxi and secretary gangs, which operate within the civilian realm.

The PLA factions, accused by some of siphoning off defence funds, are blamed by some veterans for turning the military into a system where officers are promoted not for their skill or accomplishment, but for the financial favours they can arrange or offer. This has allowed incompetence to thrive at senior levels, they say.

Guo entered the army in 1961 and was placed with the PLA’s 55th Division of the 19th Army in the Lanzhou military command.

He never gained combat experience, unlike his CMC vice-chairman predecessors such as Zhang Wannian, Chi Haotian or Cao Gangchuan, who either served in the Korean war, fought in China’s border skirmish with Vietnam in the 1970s, or underwent advanced training in specialised fields within the former Soviet Union.

By the 1990s, Guo had been elevated to commander of the influential 47th Army Corp in Lanzhou in Gansu province and in 1993 was made deputy commander of the Beijing military command.

After his address was allegedly overheard by Jiang, he returned to Lanzhou as its top military chief in 1997 and the previous commander was forced to step aside.

“Liu Jingsong was supposed to stay in Lanzhou one year more until he reached the retirement age at 65, but he had to give way to Guo under Jiang’s order,” said the source close to the military science academy.

Two years later, Guo was promoted to deputy chief of the PLA’s General Staff Department, one of the military’s four headquarters, in charge of weaponry build-up, training drills and strategy – a position that also conferred membership in the CMC.

When Hu came to power as party general secretary in 2002, Jiang held on to his chairmanship of the Central Military Commission for two more years. He eventually moved aside, but continued to dominate its affairs, through his proxies Guo and Xu, military insiders said. Guo was promoted to deputy chairman in 2002 and Xu in 2004.

Change began to come in the highest ranks of the military after the Politburo Standing Committee elected Xi as a third vice-chairman of the CMC in 2010.

It’s widely believed within military circles that Hu conveyed to Xi that Jiang had tied his hands when it came to taking on entrenched interests within the PLA, but Xi might succeed where Hu had not.

The new leader came from a princeling background – his father was one of the first-generation of Communist Party leaders Xi Zhongxun – and Xi himself had experience in the PLA bureaucracy – he served as a secretary to a former defence minister, Geng Biao .

When Hu handed power over to Xi, the retiring leader stepped away from the CMC, the first time in several decades both the presidency and the CMC chairmanship were given up simultaneously, which strengthened Xi’s hand.

The PLA factions were put on notice last year, the Shanghai-based retired senior colonel said, when the PLA Daily began regularly publishing full-page speeches by CMC members and regional military leaders.

Xi was giving the cliques a chance to “straighten up” and decide where their allegiances lay, the Shanghai-based senior colonel said.

Many of Guo’s former subordinates pledged loyalty to Xi. After Xu was taken down in March, 2013, suspicions intensified that Guo would be next.

Beginning in November, key members of his faction began to fall.

Lieutenant General Ma Faxiang , former deputy commissar of the navy, committed suicide on November 13, 2014. Former personal secretary Major General Lai Ceyi , who was deputy commander of the quasi-official Xinjiang Production and Construction Corps, was removed from office in January, local media have reported. Around the same time, former protégé Lieutenant General Fan Changmi , an ex-deputy political commissar of Lanzhou military command, was also taken away, the PLA Daily reported. Untouched so far are deputy head of the General Political Department Du Jincai , General Staff chief Fang Fenghui , and the head of the Guangzhou military command Xu Fenlin , among others.

The announcement of probes into Major General Guo Zhenggang , Guo’s son, among one of 14 senior officers for suspected “legal violations and criminal offences” by the PLA Daily in March, as well as the junior Guo’s relationship with his wife Wu Fangfang’s now-defunct land development business, have further exposed details of the Northwest faction to the public.