In his first two terms as commander of the world's largest military, Chinese President Xi Jinping has unleashed sweeping changes to its structure, posture and potency.

Over those 10 years, China has rapidly expanded and advanced its naval and rocket forces, purged thousands of officers over corruption, reformed its command operations and built bases deep in the maritime heart of Southeast Asia.

Now come the tricky next steps for his Central Military Commission: implementing sweeping changes to its leadership, which commands China's two million-strong People's Liberation Army, potentially tightening Xi's grip over the military and its modernisation.

Yesterday, China's Communist Party kicked off its once-in-five-years congress, where it is expected to name replacements for four retirees among the six senior officers who serve under Xi on the commission. Among those expected to step down are the body's vice-chairpersons, Generals Xu Qiliang and Zhang Youxia, both 72. Zhang is widely viewed as a close Xi ally.

Their replacements must integrate increasingly complex forces that would be vital for a Taiwan invasion, say eight Asian and Western military attaches and seven security analysts, fulfilling Xi's long-held demand that the military can "fight and win wars".

Diplomatic challenges are also mounting, as China's military modernisation confronts the traditional US strategic dominance in East Asia.

The military envoys and three of the analysts say the commission will need to secure foreign base and port access for its expanding naval fleet as well as tackle possible external pressure to deepen international engagement over its arsenal of nuclear weapons. A slowing economy could also complicate modernisation.

Amid all those challenges, most of the incoming generals are likely to lack one element that marked at least some of their commission predecessors: combat experience.

Zhang and commission member General Li Zuocheng, who is also expected to retire, are some of the last two serving officers to have fought in the bloody border conflict with Vietnam that started with a troubled Chinese invasion in 1979 but rumbled on until the late 1980s.

Potential replacements include recent commanders from the reformed Eastern and Western theatre commands, responsible for Taiwan and the Indian border respectively, eight envoys say. Promotions also could come from the Southern Theatre command, home to vital naval bases.

Who is chosen could shed light on Xi's military priorities. Any operational choices are almost certainly to be balanced by political commissar promotions, given their ongoing role to ensure the military serves the Communist Party, rather than the country.

Operating out of an imposing and well-protected command building in Western Beijing, the commission sits nominally under the party's Central Committee but in practice works closely under the Politburo's Standing Committee. Xi heads both bodies.

That overlap means has led some analysts to caution against predictions of a Taiwan invasion based on any new commission lineup. The Standing Committee, not ambitious generals, would make such a momentous decision, they say.

"There is no shortage of senior military officers who internally parrot Xi's 'fight and win' mantra, but the conundrum for the PLA is the lack of operational experience," said Alexander Neill, a private military analyst.

James Char, a security scholar at Singapore's S Rajaratnam School of International Studies, said the PLA suffered from "shortcomings" in combined arms and joint operations.

"Its capacity for sustained power projection also remains limited at present," Char said.

China's Defence Ministry did not respond to requests for comment.

Loyalty to Xi is crucial

The importance of absolute loyalty to Xi is crucial.

Four diplomats scrutinising developments expect to see the continued rise of veteran commissar Admiral Miao Hua, head of the commission's Political Work Department, to one of the Vice-Chair positions.

Miao, who has early links to Xi when both were posted in coastal Fujian province opposite Taiwan, will almost certainly be balanced by a more operational commander, possibly Army general Liu Zhenli.

Two officers recently promoted to staff roles at the commission are also being watched, recent Eastern and Western commanders He Weidong and Xu Qiling. Xu Qiling also has experience in Taiwan operations.

The August drills around Taiwan after US House Speaker Nancy Pelosi's visit to Taipei showed the PLA still had only limited abilities to fully integrate its forces within and across commands - the so-called "jointness" that Xi is eager to promote.

Senior Pentagon officials recently reiterated assessments that they did not think China would invade Taiwan in the next two years.

US officials have privately said that they do not believe China will be militarily ready to fully take Taiwan by even 2027.

Nuclear focus

For some diplomats and scholars, the growing importance of the commission is highlighted by China's nuclear forces, which Pentagon assessments say are expanding at a faster-than-expected rate.

Over Xi's next five-year term, China is expected to have up to 700 deliverable nuclear warheads, and 1,000 by 2030, according to the Pentagon's latest annual report on China's military modernisation.

More of those weapons are expected to be kept in an advanced stage of readiness in modernised silos. China now appears to operate a "nuclear triad", capable of launching missiles from land, aircraft and submarines, the report notes.

Christopher Twomey, a security scholar at the US Naval Postgraduate School in California, said it was important to resume international exchanges to better understand Beijing's evolving nuclear doctrine, despite the growing role of habitually suspicious commissars on the commission.

"The new CMC will have an important voice on whether to engage the US on ensuring the US on ensuring stability in the strategic nuclear arena," Twomey said. "One suspects that leaders from the political side of the force would be most suspicious, whereas more international-minded officers might have some awareness of the dangers of spirals and inadvertent escalations."

- Reuters