Zimbabwe, a country born from the inferno of a seven-year guerrilla war, has embarked on the difficult process of forming an integrated Army from elements of the three forces that fought so bitterly.

It is somewhat akin to the U.S. government a century ago seeking to unify the Union and Confederate armies six months after the Civil War.

By the end of December -- just one year after the conclusion of the bloody Rhodesian bush war -- more than 13,000 troops are scheduled to be integrated from the rival guerrilla forces of Robert Mugabe and Joshua Nkomo and the white-led army that fought them to maintain white power in the southern African nation. Other joint units are to be formed next year, bringing the total professional force up to about 20,000.

Persons familiar with the program, including whites who are quitting the military, say privately that it has been trouble-free so far.

They hedge their remarks by noting that there have been a number of violent clashes involving dissidents from the former guerrilla armies. None of the incidents, however, has involved troops participating in the integration process.

If the program succeeds, it will be a major achievement for the country's first black-majority government led by Prime Minister Mugabe. A unified Army would help greatly to return the country to peace and stability, thus encouraging foreign investment and aid.

Some of the problems faced in the integration program are:

Years of racial bitterness over the issue of black-majority rule.

Traditional tribal hostilities between Mugabe's Shona-based forces and Nkomo's troops, who are dominated by the minority Ndebele tribe.

The need to convert the former guerrillas from a political force into a professional army loyal to the government of the day.

The fears of many soldiers that they would not be able to find a place in the new Army since Zimbabwe, as a result of the war, still has upward of 55,000 people under arms in a nation of only about 7 million.

Both African sides held back their best troops when the integration process began in February while the country was still under temporary British administration, the source said.

Since then, five 1,000-man battalions have been formed with equal numbers from Mugabe's and Nkomo's forces. Four more such battalions are to finish training by December. These are to be joined by three from the former white-led Rhodesian Army to form four brigades. Integration at the battalion level is scheduled for next year. f

This, according to a white former Rhodesian colonel, could be "a major stumbling block." Other sources said that the desire by all to stay in the military should help in carrying off the unification successfully.

Already there are a number of cases of informal integration. Members of the Rhodesian African Rifles and their white officers are patrolling with units of the new Army since Mugabe deployed them last week to help the police in putting down violence.

The integrated forces are having to deal with their former comrades in arms, but a military source said that "there is no question they work for the state. They are not political animals."

A major shootout could test this belief, however.

One stablizing factor for the training program, in which 130 British military specialists are assisting, is that there has not been the mass exodus of white personnel that had been widely expected in the event of a Mugabe victory.

By the end of the year, about 30 percent of the approximately 2,000 white regulars in the former security forces will have quit, according to informed sources. The expectation is that by the time the exodus winds down about 1,000 will remain -- substantially more than most whites would have expected.

The most objectionable units to blacks such as the Special Air Services and the Selous Scouts, which carried out cross-border raids, and the all-white Rhodesian Light Infantry are being disbanded.

Conscription, which took in upward of 1,000 whites a year during the war, has been ended with the last draftees scheduled to be released by March. Ten thousand white reservists are still technically liable for active duty for more than six months a year, but, in effect, the system is being allowed to lapse with only a few needed specialists being called up.

The recently retired colonel, who asked not to be identified, said most of the whites who were bitter about the outcome of the war had already gotten out of the Army.

"The rest," he said, "have swallowed what they had to and are willing to serve under black leadership."

He got out because he didn't see much future for a white officer and because he couldn't adjust to a peace-time Army, a common factor in many resignations, he said.

The ex-officer praised the attitude of the former guerrillas in the training program. Most white soldiers had only scorn for the guerrillas during the war, but that attitude has changed since the two sides have gotten to know each other.

The former guerrillas are reported to have adapted readily to the British spit-and-polish tradition familiar to the Rhodesian forces. Over time the tradition is bound to be modified, however, in view of Mugabe's leaning toward a Chinese-style army designed to play a role in agricultural and community development.

The Army has already embarked on the Chinese model with the launching of operation SEED (soldiers employed in ecomonic development).

Some 9,000 soldiers are already involved in three agricultural projects and eventually it is hoped that the program will absorb upward of 30,000 troops who will not qualify for the regular force. But many of those may not be content with being farmers or builders with only a nominal role in the Army.

Currently there are 32,000 former guerrillas either being integrated or in the process of being moved to urban townships from assembly points set up in the countryside last year. There are still about 11,000 members, predominantly black, of the former Rhodesian Army and as many as 10,000 guerrillas outsidethe country where they were sent for training before the end of the war.

There seems to have been little adverse effect on the integration caused by the firing of Gen. Peter Walls, the former Rhodesian commander who headed up the integration but then turned sharply critical of Mugabe.

Mugabe has let the matter rest for the time being with four commanders -- Rex Nhongo of ZANLA, Lookout Masuku of ZIPRA, Rhodesian Army Gen. Sandy Mclean and Air Marshal Frank Mussell -- all having equal status on the joint military command.

Picking a single commander, however, could be a thorny issue in the future, emphasizing the void left in Mugabe's ranks when his popular, widely respected commander, Josiah Tongogara, died in a collision in Mozambique just before the war ended last December.