Prime Minister Robert Mugabe no doubt is relieved that his arch rival for power, Joshua Nkomo, has fled Zimbabwe. This seems effectively to eliminate Mr. Nkomo as a continuing political threat. But the problem of internal dissension will not likely go away soon. It will take the highest measure of statesmanship on Mr. Mugabe's part to begin to heal the tribal animosities of that riven land and to demonstrate that he intends to forge a united country in which blacks of every ethnic background - and whites - can live and work together peaceably.
Tribalism is an insidious phenomenon wherever it rears its head - from Northern Ireland to Indochina - and the young country of Zimbabwe has had its share of grief because of it. This is not altogether surprising, for it takes a gradual cultural and social evolution to overcome deep-seated ethnic feelings - in this case between the majority Shona-speaking blacks and the minority Ndebele people led by Mr. Nkomo - and to learn to share power. Having won their united struggle against white minority rule three years ago, the blacks still have to work out their tribal-related political rivalries.
Mr. Mugabe cannot be blamed for trying to put down violent dissent. He had offered Mr. Nkomo, the loser in the first black rule vote, the ceremonial post of president in 1980, but this was turned down. And, although Mr. Nkomo was brought into a coalition government, members of the two former guerrilla armies began clashing and pro-Nkomo political dissidents tried to use force to restore their party's position. When huge arms caches were found on farms belonging to Mr. Nkomo's party, and a wave of banditry swept through Matabeleland, Mr. Mugabe seemed to have little choice but to move in with force. However, he provoked justified criticism by sending in a North Korean-trained brigade drawn from the ranks of the Shona, a mission that apparently led to widespread massacres.
In the face of such bloodshed, political reconciliation may not come easily. Prime Minister Mugabe may have to go an extra mile - in economic help and political magnanimity - to persuade the Ndebele minority that they are not the disadvantaged and oppressed segment of Zimbabwean society. Mr. Mugabe's ultimate objective is single-party rule brought about through peaceful merger of the two leading parties, but a precipitate move now to finish off Nkomo's Zimbabwe African People's Union (ZAPU) would exacerbate tensions. Simply requiring that the party rid itself of violent dissent could help stabilize the situation.
Let the rest of the world not view the turmoil in Zimbabwe with a ''we told you so'' condescension. Tribalism is a powerful force to overcome, but, as the experience of Kenya and Ivory Coast (and indeed post-Tudor Britain) bears out, it can begin to give way to a broader, national consciousness given time and effort. Zimbabwe, moreover, after long years of civil war and a revolutionary change of government, has made creditable strides toward building nationhood. And this in the face of economic stress and external dangers.
Zimbabwe will pull through if Mr. Mugabe chooses the practical path of accommodation - and shows that he means to be leader of all the people. The Ndebele, for their part, will help their own lot if they display a willingness to give the prime minister a chance.