Tribalism, variously described as the curse or motor of African politics, is often viewed as one of the main factors responsible for the multiple divisions among Zimbabwean nationalists.

This is only partly true and it is impossible to understand the infighting among them in tribal terms only.

There are two main ethnic groupings in Rhodesia separated primarily by language and history. The largest are the Shona, or Mashona, who are subdivided into five main tribes-Karanga, Zezeru, Manyika, Korekore and Ndau. Together with the separate but also Shona-speaking Rozwl, the Shona family makes up 77 percent of the total black population of Rhodesia.

The other grouping is the Ndebele, consisting of Ndebele people proper and the linguistically and ethnically related Kalanga. Together, they account for almost 20 percent of the total.

The Ndebele, an offshoot of the Zulu people of South Africa, live almost entirely in the southwest along the Botswana border, from Victoria Falls down to Beitbridge. Bulawayo, Rhodesia's second-largest city, is their principal urban center.

The Shona live all over Rhodesia, are predominant here in the capital, and out number the Ndebele even in Bulawayo.

The Ndebele have traditionally been regarded as the more warrior-like of the two because they fought and subduded many of the Shona tribes upon their arrival to what is now known as Rhodesia in the 19th century.

Both recognizing and encouraging this traditional Ndebele-Shona rivalry, the British and the Rhodesian whites divided the country into two main african regions-Matabele and Mashonaland.

It is the prevailing, simplified view that the nationalist guerrillas are basically divided along ethnic lines, with Joshua Nkomo's Zimbabwe African People's Unon (ZAPU) grouping the minority Ndebele and Robert Mugabe's Zimbabwe African Nation Union (ZANU) the majority Shona.

This is far more true of the rank-and-file guerrillas than of the two parties' leadership, particularly Nkomo's ZAPU. Nkomo's army is probably 80 percent or more Ndebele in origin and Mugabe's is in the same proportion Shona.

The top People's Union leadership, however, has a very high proportion of Shonas. Although Nkomo is the acknowledged leader of the Ndebele people, ZAPU Vice President Josiah Chinamano, national chairman Samuel Munodawafa, secretary general Joseph Msika, and publicity secretary Willie Musarurwa are all Shona or were brought up in Shona speaking areas of Rhodesia.

The presence of so many Shonas in ZAPU's top ranks has proven both a strength and weakness at times.It has given the People's Union an appeal and standing among many Shonas it would not have had otherwise, but it also has led to considerable tension between the Shonas who dominate the political side of the party and the Ndebele or Kalanga in the military command.

The top leadership of Mugabe's National Union is far more homogoneously Shona, but that has not spared it from bitter and bloody rivalries among Karanga, Manyika and Zezeru, particularly for the top military posts.

This struggle only highlights one of the basic truths-and confusions-about the faction-ridden nationalist movements: the many rifts within the Shona-speaking people. They run even deeper than the various tribes, however, to involve feuding tribal clans and even smaller subgroups born under the same totem, or extended family emblem.

Some examples:

The most important intratribal split is within the Karanga people, the largest Shona subgroup comprising 22 percent of the total black population, according to Rhodesian tribal experts. The Karanga have to a great extent replaced the Ndebele as Rhodesia's leading warriors.

The vast majority of black soldiers in the Rhodesian security forces-60 percent of the police alone-is Karanga. At the same time, the top leadership of Mugabe's guerrilla army, including its commander in chief, Josiah Tongogara, and a good number of the rank and file are also Karanga.

The Manyika, 13 percent of the total population, are just as badly divided. Bishop Abel Muzorewa, the prime minister-elect of the new black government, is a Manyika. But probably more Manyika, who live along the Mozambican border, are backing Mugabe than the bishop.

Intra-Shona rivalries and tensions could become a major divisive element within the bishop's government in the future. It is widely believed-some say already documented-that Muzorewa put members of the Manyika tribe at the head of the party's list of candidates in all eight electoral districts for the April elections. As a result, the vast majority of the 51 deputies the party will have in the new Parliament will be Manyika.

The Zezeru, led by James Chikerema, the bishop's leading critic within his own party, are said to be particularly bitter about this, although they are still represented in the Parliament. Together with the Karanga, who form the backbone of the Army, they could form a coalition against Muzorewa and seek to oust him, according to one theory circulating in Salisbury among disenchanted blacks. CAPTION: Map, no caption, By Richard Furno-The Washington Post