Xi is trying to secure the devotion of China’s military

To remedy that, Xi has launched a campaign to reshape minds in one of the world’s largest armed forces. Since he ordered the indoctrination drive last summer, China’s two million soldiers, sailors and airmen have been studying Xi’s speeches, learning Communist Party rules and seeking inspiration from revolutionary exploits.

Military leaders hammered home the message in a six-part documentary, “To Harden With Fire," showcasing heroic exploits, new capabilities and cutting-edge weapons—and arranged screenings for the rank and file.

“We must uphold the party’s absolute leadership over the military," Xi told senior commanders at a June conclave when he launched the indoctrination campaign. “The gun barrel must always be grasped by people who are loyal and reliable to the party."

The campaign is meant to boost discipline and patriotic fervor as Xi presses ahead with his sweeping purge, which has battered morale and raised questions about China’s ability to build a modern fighting force.

Whether Xi can enforce loyalty without undermining military readiness could shape the outcome of China’s quest to become a first-rate military power that can protect its global interests, compete with the U.S. for strategic dominance and potentially seize Taiwan, the self-ruled island that Beijing claims as its territory.

For China’s leaders, the military is also the ultimate guarantor of Communist Party rule and their personal authority. The People’s Liberation Army swept Mao Zedong to power in 1949, helped Deng Xiaoping crush the 1989 Tiananmen Square protests, and remains an influential constituency in Chinese politics.

The party enforces control over the armed forces through political officers, who share decision-making authority with military commanders and can veto orders that are seen as contrary to the party’s priorities—a Soviet-influenced arrangement known as the dual-leadership system. Major units have party committees that can decide important matters including combat, training and personnel.

The emphasis on political control, some experts say, could end up undercutting China’s ambitions to challenge Western military might.

“If you’re spending time on political education, that’s time you could have spent training, practicing and preparing to fight," said Phillip Saunders, director of the Center for the Study of Chinese Military Affairs at the National Defense University in Washington, D.C. “Ideological indoctrination is a tax on military preparedness."

Since taking power in 2012, Xi has used anticorruption purges to assert his authority and advance plans to modernize a military that hasn’t fought a full-scale war since 1979. The goal is to create a more nimble, 21st-century force that can integrate air, sea and land operations, project power and wage war in the digital age.

Xi tossed out dozens of generals during his early years as leader, replaced them with officers whom he considered to be more professional and politically reliable, and overhauled the military’s command structure to put himself more firmly in control.

He ramped up defense purges again in the summer of 2023, starting with officers commanding China’s nuclear arsenal, reaching into the military’s highest echelons and defense contractors that produce stealth fighters and other advanced armaments.

More than two dozen senior PLA officers and defense-industry executives have been placed under investigation or removed from public office over the past year and a half, according to official disclosures reviewed by The Wall Street Journal. Other officers and executives may have been purged in recent months, analysts said, noting their unexplained absences from high-profile meetings.

Prominent targets included a top admiral who was considered a Xi protégé and oversaw political indoctrination, and a defense minister and his predecessor. Senior executives in the defense industry have come under investigation or disappeared from view, including the chief designer of the J-20 stealth fighter—China’s rough equivalent to the American F-22—whose biography vanished from his company’s website in recent months.

Xi ordered the military indoctrination drive in the midst of this crackdown. Units across the country leapt into action, running seminars, quizzes and essay contests. Some arranged pilgrimages to revolutionary sites and cultural shows to celebrate the history of the PLA ahead of its centennial in 2027.

The military’s flagship newspaper, PLA Daily, launched a front-page column to document how combat forces and support units were channeling Xi’s ideas in lectures, combat drills and field operations.

The Central Military Commission, which commands the armed forces, approved two new anthologies of Xi’s remarks on political discipline in the military for all personnel to study. The commission launched a new education campaign this month on the theme of “forging political loyalty and fighting hard battles well."

Key themes include the need for unwavering commitment to Xi’s leadership and his military modernization program.

In China, ideological education has been a staple of military training since the Mao era, aimed at deepening loyalty to the Communist Party. Current guidelines generally require military units to spend 42 to 54 days a year on political indoctrination, including at least one session a month.

Under regulations updated in 2020, major formations at the brigade level should allocate no less than 20% of their annual education time to “ideological and political" training, while smaller combat units must devote at least 40%.

Political officers often arrange weekly sessions to discuss party policies with service personnel. One army brigade in central China had its troops study Xi’s military directives in daily sessions meant for consuming the news.

Xi’s emphasis on indoctrination, alongside corruption purges, could set back his plans to modernize the military, according to M. Taylor Fravel, director of the Security Studies Program at the Massachusetts Institute of Technology.

“The purges, along with the ideological campaign, can induce much greater caution into decision-making within the PLA at all levels, as officers will worry about making the ‘wrong’ decision that could expose them to punishment later," Fravel said. “This dynamic likely extends to China’s defense industries, too."

The military has in the past warned against excessive political education, citing its impact on readiness. When one air-force unit ran 132 ideological classes in 2020, sometimes four lessons in a day, its personnel became “overwhelmed with education," the PLA Daily reported.

Xi has repeatedly stressed the party’s pre-eminence in military affairs, telling senior commanders in June that they must “integrate the party’s leadership into all aspects and processes in war preparation and warfare."

Chinese state media have at times acknowledged issues inherent to the military’s dual-leadership system, such as by questioning the military competence of political officers and criticizing their perceived subpar understanding of tactics and operational matters.

Some units have tried to address this problem by putting their political officers through combat-skills competitions, testing their ability in matters such as marksmanship, fitness and field tactics. One brigade did so last year after finding that its political officers were showing “weak battlefield awareness" and “insufficient military literacy," according to the PLA Daily.

Such training, however, doesn’t address a fundamental issue with the dual-leadership system. The need for unit commanders to justify themselves to political commissars “slows down your decision-making and reaction time in combat," said Saunders, the National Defense University researcher. “It might lead to suboptimal decisions, if they have to always look over their shoulders."

Write to Chun Han Wong at chunhan.wong@wsj.com