Breaking with Pretoria. White South Africans become foot soldiers for the army of the African National Congress

The long-established presence of whites in South Africa's outlawed African National Congress (ANC) is undergoing an important change: Their contribution as strategic planners, agitators, and couriers is being supplemented by their role as combatants on the front line. This trend was reaffirmed by the arrest last week of four whites on suspicion of having been recruited and trained to fight for Umkhonte We Sizwe (the Spear of the Nation), the ANC's military arm.

The change first became evident in 1986 with the arrest and conviction of two young white ANC recruits: Eric Pelser, a draft dodger, and Marion Sparg, a former journalist. Mr. Pelser was jailed for seven years and Ms. Sparg for 25.

The Pelser and Sparg trials highlighted a change in the function of whites in the ANC, according to a highly placed intelligence officer and Tom Lodge, an expert on the ANC. Both the ANC recruits received training in camps run by the ANC in Angola; and they were the first known white recruits to Umkhonte.

Before that, another young white, Hein Grosskopff, scion of a respected Afrikaner family, was named by the police as the suspected ANC bomber in a deadly blast in Krugersdorp in March.

There has been a continual white presence in the ANC from the time it went underground in 1961 to last week's arrest of the suspected ANC quartet on a small farm near Pretoria. The banning of the ANC in 1960 presaged the formation of Umkhonte. Among ANC activists jailed for life in 1964 was one white.

Whites who have served in one capacity or another include Joe Slovo, former chief of staff of Umkhonte, and Ronnie Kasrils, who, according to the security police, plays a key role in recruitment and training of ANC agents.

But according to the intelligence officer, the emergence of young white Umkhonte fighters is a new development. Umkhonte recruits are known as MKs (MK is the Zulu abbreviation for Umkhonte We Sizwe). Until 1986, MKs were assumed to be black.

The appearance of white MKs poses several questions:

How important are they to the ANC?

What special opportunities do they offer the ANC high command in its ``armed struggle.''

What kind of people are they, and why did they join the ANC?

``Whites are very important to the ANC,'' says the intelligence officer. They give credence to its self-projected image as a nonracial organization, he adds. The ANC opened its national executive committee to whites for the first time in July 1985, having already opened membership to all races in 1969.

Whites are also vital because they nurture the ANC objective of dividing the white community against itself, and they can undertake missions that are more difficult for blacks, who are more visible.

White ANC agents are said to have rented the conveniently situated house in which an attack on South African military headquarters was planned in 1981.

White MKs are valuable to the ANC for yet another reason, the intelligence officer says. They are generally better educated than blacks and thus better able to plan sophisticated attacks.

White recruits to the ANC are drawn from a small social base, Dr. Lodge says. Most are middle class. Many have a history of lawful protest in left-wing movements. All have become appalled by South Africa's race policy and convinced of the futility of legal opposition.

Afrikaners who become pro-ANC arguably have a different experience. They are, in general, uncomfortable in liberal circles dominated by English-speaking compatriots. Because they know Afrikaner power from the inside, they feel ``the need to take a hard stand,'' says Nico Smith, an activist Afrikaner clergyman.

White ANC recruits and suspected recruits have another common element: They are often draft dodgers.

For some young men the choice seems to be conscription into the South African Defence Force or joining Umkhonte. Pelser, in a court statement, told how, repelled by the thought of service in the SADF, he fled the country and eventually joined Umkhonte.

Andrew Prior, a professor at the University of Cape Town, offers a different perspective on the same theme: Draft dodgers move into a different environment when they flee, one in which the South African state appears about to collapse, and, influenced by that view, they join the ANC's military arm in the belief that they can contribute to the ``one last push'' needed to bring the order down.

The intelligence officer contends that most white MKs are social misfits. And Professor Prior questions whether most white recruits are not what Leon Trotsky contemptuously called ``bourgeois adventurists.'' He asks whether they are not trying to deny their class role in repressing blacks and assuage uneasy consciences through ``highly symbolic, high-profile actions.''

But while some captured white ANC recruits reject their past convictions as ill-considered or immature, many insist that they are combatants who did their duty in a situation where they had to choose sides.