Outwardly, China’s military has never been stronger. Its naval ships venture farther across the oceans. Its nuclear force grows by about 100 warheads every year. Its military flights around Taiwan are increasingly frequent and intimidating. Every few months, China unveils new weapons, like a prototype stealth fighter or newfangled landing barges.

Internally, though, China’s military is experiencing its most serious leadership disarray in years. Three of the seven seats on the Central Military Commission — the Communist Party council that controls the armed forces — appear to be vacant after members were arrested or simply disappeared.

That internal turbulence is testing the effort by President Xi Jinping, going back more than a decade, to build a military that is loyal, modern, combat-ready and fully under his control. Mr. Xi has set a 2027 target for modernizing the People’s Liberation Army, or P.L.A., and also — according to some U.S. officials — for gaining the ability to invade Taiwan, which Beijing claims as its territory.

The current wave of investigations and removals has reached some commanders handpicked by Mr. Xi, suggesting recurrent problems in a system that he has tried for years to clean up. In the first years after Mr. Xi came to power in 2012, he launched an intense campaign to clean up corruption in the military and impose tighter control, culminating in a big reorganization.

“When Xi Jinping sees his own men making mistakes, he is likely to be especially furious,” Joseph Torigian, an associate professor at American University who has studied Chinese leaders’ relations with the military, said of Mr. Xi. “Control over the military is so existential. It’s inherently explosive. That’s why any sense of stepping out of line has to be crushed.”

The most jarring absence in the military leadership is that of Gen. He Weidong. The second most-senior career officer on the Central Military Commission, General He has disappeared from official public events and mentions, an unexplained absence that suggests he, too, is in trouble and may be under investigation.

Another top commander, Adm. Miao Hua, who oversaw political work in the military, was placed under investigation last year for unspecified “serious violations of discipline,” a phrase that often refers to corruption or disloyalty. He was among around two dozen, if not more, senior P.L.A. officers and executives in the armaments industry who have been investigated since 2023, according to a recent tally by the Jamestown Foundation.

Both men had risen unusually quickly under Mr. Xi’s patronage. While Chinese officials are vulnerable to investigations for corruption or disloyalty even in the best of times, for him to lose them both reveals an uncommon degree of top-level upheaval.

“The purges may have affected the working of the bureaucracy. It can also create a broader skepticism about the readiness of the Chinese military within the leadership,” said Ely Ratner, who had been an assistant secretary of defense in the Biden administration.

Mr. Xi’s ultimate fears for the Chinese military come from questions of battlefield preparedness, and anxieties that commanders could drift away from absolute loyalty to him and the party. Mr. Xi may seek a fourth term as leader of the Communist Party in 2027, and he will need to replace retiring or purged commanders with a new cohort whose devotion to him is beyond question.

Recent official statements point to a renewed drive to reinforce ideological control. The Central Military Commission issued new rules last month aimed at “fully eliminating toxic influences, and restoring the image and authority of political officers.” A series of front-page commentaries in the Liberation Army Daily — the main newspaper of the Chinese military — urged P.L.A. political officers to observe absolute loyalty.

Since Mao Zedong’s era, the military has served not only as a fighting force but also as a lever of political control for Chinese leaders, as their ultimate protection against potential rivals or popular uprisings. In internal speeches to the military throughout the earlier years in his rule, Mr. Xi praised the army for standing by party leaders during the 1989 military crackdown on pro-democracy protests, according to a volume of his speeches to the military published in 2019.

But in such speeches, Mr. Xi has also repeatedly cited the lessons of Xu Caihou and Guo Boxiong, the two most senior former P.L.A. commanders who were arrested for corruption nearly a decade ago. If the rot in the Chinese military elite had been left to spread, “our forces would have become a private army under certain people, an armed force turning against the party,” Mr. Xi told a Central Military Commission meeting in 2018.

There are no signs that the recent turbulence in the military amounts to concerted defiance of Mr. Xi. But even relatively few cases of corruption or mismanagement could erode the trust between Mr. Xi and his commanders, said Joel Wuthnow, a senior research fellow at the National Defense University in Washington who studies China’s military.

Mr. Xi is the only civilian party leader who sits on the Central Military Commission, which ensures his singular power over the military. That also means that he cannot turn to other civilian officials to help him.

“Xi would have to rely on commanders to develop options and implement them based on a huge amount of information and technical skills,” Professor Wuthnow said. “If he’s unable to verify that those people are honest, professional and competent, then I think his appetite for war goes down because: How can he be sure of the outcome?”

The purges are likely to disrupt coordination, weaken confidence in commanders and prompt Beijing to be more wary of considering an amphibious assault on Taiwan, M. Taylor Fravel, a professor at the Massachusetts Institute of Technology, wrote recently in Foreign Affairs.

“The high intensity kinds of operations that would be involved in an invasion of Taiwan, or a blockade of Taiwan — pretty much anything that would happen under the shadow of U.S. involvement — I think will be impacted for a period of time by these problems,” Professor Fravel said in a telephone interview.

But the need to act strongly in a crisis against foes might override any doubts about combat readiness, Professor Fravel said. If Mr. Xi felt that a war on Taiwan was necessary, he would most likely not hesitate to send his armed forces into battle, whatever the gaps in the top command, Professor Fravel said.

As if to make that point about resolve, Mr. Xi has pushed China’s forces to perform increasingly demanding operations, such as the recent exercises by two aircraft carriers and accompanying warships in the western Pacific. An intercontinental missile test that arced over the Pacific last year appeared partly intended to send a similar message of resolve. “There is no detectable delay or scaling back,” in Chinese naval operations, said Andrew S. Erickson, a professor at the U.S. Naval War College.

Next month, Mr. Xi will preside over a military parade in Beijing to showcase China’s forces and his authority over them, when the party commemorates the 80th anniversary of the end of World War II, which China celebrates as its victory over Japanese conquest.

In the lead-up to the parade, the Chinese state broadcaster released a new documentary series called “Storming the Fort” that depicted the armed forces as primed for combat. “When the party tells you to do something, you sure do it,” an infantry officer says.