`Big prize' for southwestern Africa. The signing of accords on Angola and Namibia marks the end of an eight-year effort for the American mediation team. But peace in the region will not be assured until all Cuban and South African troops have returned home - and an end is found to Angola's 13-year civil war.

Today at the United Nations in New York, an eight-year American mediation effort pays off. South Africa, Cuba, and Angola are to sign a complex set of accords designed to bring an end to the international wars that have beset that part of the world for 13 years.

Peace is not yet assured. The accords have to be carried out: Namibia has yet to reach independence, and the 50,000 or so Cuban troops in Angola have to go home. And a solution to Angola's bitter civil war still lies ahead.

But in the words of the man who has led the United States mediation team since 1981, today's signing is ``a big stake, a big prize.''

For Chester Crocker, assistant secretary of state for Africa, it's been a long, difficult journey. The process stalled repeatedly and was dead in the water for several years.

During that time, Mr. Crocker was attacked from left and right over his approach to South Africa. His persistent search for a solution to the Angola-Namibia problem was criticized and belittled. What the signing mean

``This is the end of two wars and we hope a third,'' says Crocker.

The cross-border war between South Africa and Angola and the fighting between South Africa and Namibian independence forces (South-west Africa People's Organization) will be ended.

``We think it can also lay the basis for Angolans to at long last recognize that for their internal question they have no real option except for a political solution, for political dialogue and reconciliation,'' Crocker says.

Once the accords are in place, he stresses, for ``the first time in modern history South African forces [will be] back inside their borders.'' That will bring freedom and the end of apartheid to Africa's last colony - Namibia.

The accords, Crocker says, also mark the end of ``Castro's African adventure,'' begun in the mid-1970s when the Soviets were aggressively expanding their influence in the third world.

Crocker says the accords signed today reflect ``a rather remarkable case study of US-Soviet cooperation to recognize actual historical realities and work together to solve a regional problem.''

While the US continued to mediate and apply pressure to move the process along in recent months, the Soviets quietly pushed Angola and Cuba, warning that Soviet largess would not be forthcoming if they were intransigent.

US Secretary of State George Shultz and Soviet Deputy Foreign Minister Anatoly Adamishin are to be present at today's UN signing. Both superpowers are members of the joint commission created to discuss problems that arise in following the accords.

All of these factors add up to ``the most interesting and intricate'' international peace accord achieved ``in quite a long time,'' says Samuel Lewis, president of the United States Institute of Peace. These accords were made possible, he says, only by a complex mix of bilateral and multilateral diplomacy, formal and informal great-power intervention, and UN support.

On a regional level the accords could lead to changes in the way South Africa and its neighbors get along, Crocker says. But the region remains ``a caldron of potential problems,'' which requires that the US stay involved on all sides ``to dampen down conflicts and point the way to alternatives.'' What's ahead?

After the signing, the UN Security Council will endorse the accords. Subsequently, the Secretary-General will present an updated plan for supervising Namibian independence.

A potential sticking point is the size of the UN force to be sent to Namibia. The US, Soviet Union, and others would like to reduce the size and cost of that force. But several nearby African states oppose that, fearing South African manipulation of the independence process.

The Security Council has approved a 70-member observer force to verify the Cuban troop withdrawal from Angola. Under the accords, Cuban troops will begin leaving early in the new year as part of an almost 2-year process.

The UN plan on Namibia will go into effect April 1 with the intention of holding elections for a constituent assembly seven months later.

The most challenging task ahead is to end the 13-year civil war between Angola's government and UNITA (National Union for the Total Independence of Angola). The US and South Africa support UNITA.

``We obviously hope the Angolan government will seize the opportunity now before it to put concrete ideas on the table about a dialogue and reconciliation with UNITA,'' Crocker says.

He stresses that the US is willing to play a mediating role if requested by the parties, but that Washington has not reduced its support for UNITA in the absence of national reconciliation. ``We have not traded horses with anyone on the side.... We feel strongly that UNITA warrants our support.''

US officials believe that black African states have the best chance of mediating the conflict and expect efforts by them in the weeks ahead. The process will be difficult, however.

It is quite likely that there will be more fighting before talks get under way. But these US specialists contend that neither side is in a position to gain military victory.

Lessons learned along the road to peace

When Chester Crocker became assistant secretary of state for African affairs in 1981, he brought a soft-spoken, even-tempered intensity to the emotional and seemingly intractable problems of southern Africa.

Early in the new administration, he persuaded then-Secretary of State Alexander Haig and President Reagan to try for a simple diplomatic trade-off - the Cubans out of Angola for the South Africans out of Namibia. Nearly eight years later ``Chet'' Crocker shared with the Monitor some of of the key lessons he learned along the way.

People ``tend to personalize important historical events,'' Crocker says. ``That's wrong. There have probably been a hundred people that have worked closely with me over these eight years.... It's been real teamwork. In fact, that phrase, which is very American, is the one used to describe our delegation by the other parties ... they know we are a team.''

``You've got to have a clearly defined presidential policy and a willingness to stick with it,'' Crocker says. ``President Reagan approved this approach to these negotiations in February '81 and has never walked away from it ... even when my name wasn't that popular.''

Crocker emphasizes the value ``of having something that is clear and logical and sticking with it, even if it doesn't immediately become `top of the pops.'''

Patience is important, too. ``You see the ebb and flow and see people some days just have the sense they have to prove themselves and have almost to provoke each other before they get down to brass tacks.''

Finally, a mediator has to be well informed. ``We invested a lot in learning as much as we could about the decisionmaking of the other parties, about the ways their leaders think and act.''