Zhang Youxia, a vice chairman of the powerful Central Military Commission (CMC), is targeted in a probe for serious violations of the law -- a common euphemism for corruption.

Investigations almost always end in removal.

Until recently, Zhang's abrupt sidelining was largely unexpected, due to his long military tenure and perceived closeness with Xi.

The sturdy, square-faced general was frequently pictured standing beside the president during officer promotion ceremonies as recently as December.

He had survived several previous rounds of anti-graft sweeps through the CMC since its seven-person roster was set during the last Party Congress in 2022.

Another CMC official, Liu Zhenli, is also under investigation, leaving untouched just two known members on the commission: Xi and discipline czar Zhang Shengmin.

- Military family -

Born in 1950 to a military family less than a year after Communist leader Mao Zedong declared the founding of the People's Republic of China (PRC), Zhang's proximity to power dates back to his youth.

His father Zhang Zongxun is considered a "founding general" of the PRC.

He served alongside Xi's father when the two were Communist fighters in the country's northwest.

The younger Zhang and Xi, now 75 and 72, are both "princelings" -- a term describing the children of revolutionary leaders who have benefitted from their family connections.

- Career -

Zhang joined the army at the age of 18 and moved up the ranks in a regiment headquartered in southwestern Yunnan province, which borders Myanmar, Laos and Vietnam.

He fought in border conflicts including the weekslong 1979 Sino-Vietnamese War, giving him rare combat experience.

The war, which involved around 200,000 Chinese soldiers, was the last major armed conflict fought by PLA troops, although clashes with Vietnam continued for around a decade.

Zhang later moved north and was eventually named commander of the Shenyang Military Region. He was made general in 2011, and later put in charge of arms and equipment procurement and development.

He was tapped to the CMC in 2012 when Xi became its head after ascending to the top of the Communist Party.

Battle-learned Zhang "had an aura of competence around him", said former US defence official Drew Thompson during a Chinese delegation's visit to the United States in 2012.

Officers "stood up faster and straighter when he entered a room" and Zhang "wasn't afraid to talk to foreigners", Thompson wrote in a Substack post about his encounter.

In 2017, Zhang was promoted to one of the CMC's vice chairman positions, also joining the Communist Party's elite body, the Politburo.

He assumed the CMC's senior vice chair role in 2022.

- Links to Xi -

Some analysts have described Zhang as a childhood friend of Xi, although others have questioned that claim.

Knowledge of their relationship is "limited", according to Asia Society's Neil Thomas, who studies elite Chinese politics.

The two men may have shared childhood circles in Beijing thanks to their fathers, who were both from northern Shaanxi province, but did not work together until later in their careers.

Still, the president oversaw Zhang's rise, Thomas wrote, making it "clear that Xi used to see him as a trusted colleague".

- Downfall -

Rumours of an investigation swirled days before it was announced, after Zhang and Liu appeared to miss an official meeting chaired by Xi and attended by second-ranked CMC vice chairman Zhang Shengmin.

But analysts have suggested trouble began far earlier, pointing to the purge of former defence minister Li Shangfu -- who like Zhang oversaw military equipment.

The defence ministry did not say specifically why the probe into Zhang and Liu had been opened.

However, the PLA Daily -- the Chinese military's mouthpiece -- said they were "corrupt elements" in a front-page editorial published Monday.

The "resolute investigation and punishment" of Zhang and Liu "removes roadblocks" and "squeezes out the water diluting combat effectiveness", it said.

An earlier editorial, published a day after Beijing announced the probes, said their actions "seriously undermined and violated the system of responsibility of the CMC chairman", Xi.