Why Zimbabwe's Mugabe feels unthreatened by rival's return from exile

The return of Joshua Nkomo to Zimbabwe coincides with the return of relative calm to Africa's newest nation. The opposition leader's unmolested homecoming is a clear sign that the Prime Minister Robert Mugabe is confident he can maintain stability despite his chief rival's presence, diplomatic sources in the capital city of Harare say.

When Nkomo fled five months ago, government troops were wielding an iron fist in the western province of Matabeleland to quell dissident activity among Zimbabwe's minority Ndebele-speaking tribe. The government blamed Nkomo, political leader of the Ndebeles, for the troubles.

Now the situation has changed considerably. Matabele-land is ''much calmer'' than five months ago, says one informed observer in Bulawayo, the main center of the troubled province. The Army's Fifth Brigade, allegedly responsible for the deaths of up to 1,000 civilians during the crackdown, has withdrawn. Security for the most part has been turned back over to the police, who have a far better relationship with the local population.

And Prime Minister Mugabe has stated that he did not foresee harsh treatment, such as a prison term, for Nkomo as the opposition leader returns home. At most, Nkomo might pay a ''little fine,'' Mugabe said, perhaps for certain minor violations such as leaving the country illegally.

The government's softer line toward Nkomo could be part of a deal struck between the two, but there is no evidence of that yet. Analysts say there are several reasons why the government has adopted a more benign attitude toward its chief political rival. Nkomo's influence, though still formidable, has waned during his absence, they say. And government confidence has grown as it has gained some command over the situation in Matabeleland.

The worst thing Mugabe could do, analysts say, would be to ''make a martyr'' out of Nkomo by heavily punishing him.

In Nkomo's absence, Mugabe has made some political forays into Matabeleland and made some gains there, some analysts say. At the same time, the prime minister has pressed ahead with his plan for a one-party state. Mugabe's -Zimbab- we African National Union (ZANU) party has held further talks with Nkomo's Zimbabwe African People's Union (ZAPU) about ''unification.'' But the talks are not going smoothly - partly because ZANU apparently insists that ZAPU allow itself to be swallowed up by the ruling party.

Nkomo's reasons for return are clear, analysts say. He needs to bolster his sagging influence, and must provide a new sense of direction and leadership to ZAPU. Of immediate concern is the government's vow to seek his expulsion from Parliament for missing too many sittings during exile.

There is speculation that Botswana President Quett Masire played a role in paving the way for Nkomo to return to Zimbabwe. Botswana's wishes are important because most analysts feel Zimbabwean dissidents pose a long-term threat only if they are allowed to have bases in Botswana.