China has announced far-reaching shake-ups among government ministers, provincial Communist Party leaders and the Army's regional commanders in recent weeks, promoting a younger generation of leaders to spearhead the country's ambitious modernization drive.

Western diplomats said the most sweeping changes so far appear to have taken place in the Army, with only three out of 11 regional commanders holding on to their old positions. The most significant of these military changes, they said, was the replacement of veteran general and Politburo member Li Desheng, the commander of the strategic northeast, which includes a border with the Soviet Union.

The recent changes of leadership are in keeping with a statement made last April by Hu Yaobang, the Communist Party general secretary, who said that 70 percent of the leaders in major party and government departments would be replaced by officials under the age of 60 by the end of this month.

Further changes are expected to occur during the next two months, culminating in a special national Communist Party conference in September. At that time, changes in the top-level 25-member ruling Politburo itself are likely to become evident. It is anticipated that several rising leaders in their fifties will replace Politburo members who are in their sixties and seventies. The average age of Politburo members is currently about 75. Several are more than 80 years old.

The veteran political chess player behind the current moves is a man who is well beyond normal retirement age, 81-year-old Deng Xiaoping, China's principal leader for nearly a decade. But the influence of Hu Yaobang, Deng's protege and expected successor, is evident in some of the moves, particularly in the promotion of several provincial party leaders.

The aim is to promote to leading positions younger, better educated, and more professionally competent officials and military officers who are suited to the country's economic modernization drive. At the same time, it now appears that Deng will continue to provide stability through this transition by retaining his position in the Politburo and his chairmanship of the party's powerful Military Affairs Commission at least through the September conference.

In many cases, technical expertise seems to count most in the backgrounds of younger officals and party leaders being promoted.

The scope of the changes -- not yet completed -- can be seen in three areas:

*In the government, nine new ministers were named last week, constituting a change in leadership of one-fifth of the government ministries and state commissions, the largest such shake-up to occur since 1982. Their average age is 55.

*In the provincial party leaderships, about a dozen new party secretaries have been named so far, including the major industrial hub of Shanghai and the strategic Guangxi region that borders Vietnam, marking a changeover of more than a third of the provincial party leaders, the biggest such change since 1983.

*In the regional military commands, the number of commands has been reduced from 11 to seven. Of the 11 commanders, eight have been retired or in a few cases, apparently shifted to other, less influential positions.

Diplomats and other observers describe the military shake-up as the biggest of its kind since regional commands were established in the mid-1950s.

As one military attache here described it, the changes amount to the "most massive military reform ever," given the plans to reduce China's estimated 4-million-strong Army by 1 million.

The shake-up is part of a longstanding effort to streamline the world's largest army. Since the mid-1970s, Deng has called the Army "bloated" and has led the drive to remove overage officers.

Last week it was disclosed that Liu Jingsong had been appointed commander of the strategic northeastern Shenyang military region, replacing veteran commander Li Desheng.

Li, believed to be about 70 years old and a one-time critic of Deng, has always been held under suspicion by some reformers because he is a survivor of the radical politics of the Cultural Revolution of 1966-76 and a leading military figure in the last years of the Maoist era.

Some foreign observers long have considered his removal to be a key test of Deng's control over the military.

Major units of the Army came under the influence of radical Maoist ideology during the Cultural Revolution, and some Army officers were reported as recently as two to three years ago to be strongly opposed to any relaxation of political and ideological controls and fearful of side effects resulting from the economic and military reforms.

Deng has made control over the military one of his primary objectives. But while their numbers may be diminishing, some Army officers are even now thought to be critics of Deng's pragmatic economic reforms and the way in which they depart from Maoist doctrine.

Deng maintains control over the Army through his position as chairman of the party's Military Affairs Commission. All of the recent changes in the military structure and commanders seem to indicate an eventual move by Deng to retire from this chairmanship. But Deng's colleagues in the leadership seem to be in no hurry for this move, apparently because of the stability he provides through his unequaled authority.

In an interview with the Hong Kong magazine Pai Hsing, published in last month's issue, Hu Yaobang emphasized Deng's continuing importance and effectiveness in the military reform process by saying that to get anything done with the Army, Hu himself and Premier Zhao Ziyang had to say five sentences, whereas Deng achieves the same result with only one.