Christian missionaries and their schools have become a prime target in a war that is dramatically changing in scope and character as nationalist guerrillas seek to show it is they who control the countryside today.

In the past three weeks, 8 missionaries and their children have been killed and at least three and possibly four mission schools with over 1,000 students closed down.

Friday, a guerrilla band visited the Elim Mission Emmanuel school deep in the Vumba Mountains along the Mozambique border and axed, clubbed and bayonetted to death eight missionaries and four of their children, including a 3 week-old baby. This brought to 33 the number of missionaries and dependents killed since the war began escalating six years ago.

Even before the Vumba massacre many of the dozen or more missionary groups working in Rhodesia were weighing whether to continue their operations in view of the rapidly deteriorating security situation.

Now the flight of missionaries from the countryside seems bound to pick up as it becomes clearer that they are being deliberately selected out for attack.

For the several thousand missionaries scattered throughout Rhodesia, it is an agonizing choice. Some of them have been working in the rural areas for 30 or more years and are extremely reluctant to deprive the African population of the only schools, clinics and hospitals available to them.

"Give us police protection and we'll carry on as before," said Ronald Bryan Chapman, director of the Emmanuel school even as the 12 bodies were being carried away and the 260 children boarding buses to return home.

"Naturally there is a concern for the missionaries safety," said Logan Atnip, head of the Southern Baptist Convention mission after the death by stabbing in mid-June of an American Baptist missionary. "But our priority is to do what the local black people desire."

The Baptists nonetheless are on the point of closing two schools with 350 children and a hospital serving 250,000 in the Sanyati tribal reserve in central Rhodesia.

As of early June, 61 African primary schools had been burned down by the guerrillas and another 709 closed for security reasons.

Many of the schools being closed, particularly the high schools, are run by the missionaries though financed heavily by the government.

At the primary level, missionaries were running over 300 schools with 90,000 pupiles in 1977, about 10 per cent of the total enrollment. They were also operating 100 high schools having 27,000 students or nearly 60 percent of the total.

Around 200 mission primary schools and a dozen secondary ones have been shut down in the past several years because of the war and the pace of closings seems to be accelerating."It is difficult to understand why they want to deny the children education," remarked A. J. Smith, a top official responsible for African education. "I still cannot come up with any explanation that makes any sense. They seem to want to destroy the fabric of education."

Earlier in the war, the two nationalist guerrilla groups, the Zimbabwe African National Union (ZANU) and the Zimbabwe African People's Union (ZAPU), regularly visited the missionary secondary schools in the backcountry for recruits. Thousands went, or were taken, across the border into Mozambique or Zambia for training.

Both groups now have more recruits than they can handle with 10,000 or more guerrillas in each of their armies. ZANU is reported to have stopped recruiting altogether.

In fact, neither group is now encouraging youths to leave the country. When guerrillas recently visited the Catholic mission school at Dett in Western Rhodesia, "they just told them to stop going to school and not to leave the area to go to school elsewhere," according to one Catholic missionary.

When they talked to the students at Emmanuel school in the Vumba Mountains Friday night, the guerrillas ordered them to go home but made no effort to take them to Mozambique four miles away.

Rhodesian government officials believe the "terrorists," as they call the guerrillas, are deliberately trying to bring about the collapse of all law and order in the countryside in their attacks on the missionaries who are often the only white people in the African tribal trust lands.

The nationalists used to blame black commandos of the Rhodesian army for the slaying of missionaries, saying it was a ruse of discredit them. Most black Africans still seem to believe it is government troops who responsible and not the guerrillas.

Yet it seems highly unlikely the government would deliberately undermine its own authority in the countryside.

Some of the missionaries see it all as a Communist assault on the Christian churches aimed at undermining their influence over the 6.8 million Africans in Rhodesia, a large proportion of whom are Christians. "The guerrillas are telling the people, 'Don't go to church,'" said one Catholic priest. "The questions the children ask after coming back from vacation show they have been receiving Communist indoctrination," he added.

Zanu leader Robert Mugabe has declared himself in favor of a Marxist state and ZAPU chief Joshua Nkomo has said he favors a socialist one in recent statements by the two leaders.

Western analysts, however, feel the reasons for the attacks are more complex, that they stem from the power struggle now under way between the new multiracial interim government and the externally based guerrilla factions and the latter's desire to show they are the ones now in control of the countryside.

"If they can stop the children from going to school, then they can also stop their parents from voting," said one analyst, referring to the new government's plan to hold elections for a black majority rule before the end of this year.

In fact, there are already grave doubts among many Africans and Europeans here that elections can ever be held in the present atmosphere of insecurity in the rural areas.

Furthermore, the closing of missionary schools and stations is seen as part of a larger guerrilla strategy aimed at uprooting all government insitutions in the countryside to replace them with their own.

ZANU leader Mugabe, himself a product of Catholic missionary education, has denied his guerrillas were responsible for the massacre at the Elim mission and said they were concentrating on military targets.

Reflecting the doubts of some black and white Rhodesians as to who is responsible for the slaying of missionaries, one Catholic priest remarked, "They may call themselves guerrills but they may simply be bandits."