When South Africa sent its bombers, helicopters, armored cars and a task force of a few thousand men into southern Angola two weeks ago, it escalated the stubborn, 15-year-old conflict it is fighting with the Namibian guerrilla movement, the Southwest Africa People's Organization (SWAPO).

The incursion was a calculated move, based on Pretoria's perceptions of its role in this region and its relationship with Washington, to pursue militarily its strategic objectives for southern Africa, where it is the dominant economic and political force.

Instead of rebuking South Africa, the United States vetoed a United Nations resolution condemning the invasion, and in a major policy speech on Africa, Chester A. Crocker, U.S. assistant secretary of state for Africa, gave notice that the United States shares several of South Africa's strategic goals.

Unless Washington now finds a way to negotiate the achievement of these goals, its stand holds within it the seeds of a future American alignment with Pretoria in a military conflict with black-ruled nations of Africa, supported by the Soviet Union. It is a position U.S. policy-makers, Republicans and Democrats alike, have been trying to avoid for 30 years.

There is no public document that neatly spells out South Africa's strategic design for this region, but conversations with military and political officials over many months provide a fairly complete mosaic. And remarks by Foreign Minister Pik Botha and Defense Minister Magnus Malan in a meeting with Crocker in Pretoria last April, a summary of which was leaked to the U.S. press, round out and confirm this basic picture.

First, the South Africans apparently do not intend to hand over power to an independent government in Namibia, which South Africa now administers, until the military and political situation in Angola is changed and the Soviet and Cuban presence there has been eliminated or neutralized.

Secondly, they want an internationally recognized role for the Union for the Total Independence of Angola (UNITA), the anti-Marxist Angolan guerrilla movement led by Jonas Savimbi.

According to the summary of their April conversation, Malan and Botha told Crocker that "having supported him this far, it would damage South African government honor if Savimbi is harmed."

Thirdly, the South Africans want to see SWAPO militarily defeated. The ruling Afrikaner elite has made a profound psychological connection between the chances of peaceful, evolutionary change at home--on its own terms and at its own pace--and its military victory or defeat, actual or perceived, in their battle with SWAPO.

It is in its war with SWAPO, a socialist, Soviet-armed movement, that South Africa feels it must show that armed struggle does not inevitably triumph, as it has in the three neighboring countries of Angola, Mozambique and Zimbabwe during the last six years.

In Namibia itself, South Africa wants an independent black government that is anti-Marxist and anti-Soviet and is not dominated by SWAPO. But if SWAPO rules, Pretoria wants a federal setup with constitutional minority guarantees and security arrangements in which SWAPO would not allow anti-Pretoria insurgents or military forces of Soviet Bloc countries to use its territory.

Finally, South African military officials are blunt about their feelings that, barring a more direct commitment by the Soviets and Cubans, they can indefinitely persevere in the war and in the end, defeat SWAPO. For Pretoria, according to the leaked summary, a low-level conflict on the Angolan-Namibian border is preferable to a Namibian civil war, which it believes would be the result if SWAPO ruled unchecked.

South Africa's recent Angolan operation appears to have been aimed at achieving these goals: creating a SWAPO-free buffer zone along the Namibian border and facilitating the westward spread of UNITA.

At the same time, the South African incursion raises the possibility of increased Cuban and Soviet involvement in Angola that conceivably could increase the likelihood of U.S. help for Pretoria.

In his policy speech in Honolulu, Crocker said that the United States "will not lend our voice to support those dedicated to seizing and holding power through violence . . . . It is essential that military force not become established as the arbiter of relations between states or the means of effecting needed political change."

He also said that "it is unlikely that the struggle between the Angolan government and opposition forces, chiefly UNITA, led by Jonas Savimbi, can be resolved militarily . . . . UNITA represents a significant and legitimate factor in Angolan politics."

Finally, Crocker said that "movement on Namibia can reinforce movement toward a Cuban withdrawal and vice versa. Furthermore, we are convinced that a satisfactory outcome can only be based on parallel movement in both arenas."

Washington's decision to go out on a limb for South Africa stems not only from its natural sympathies for Pretoria's anticommunist position, but also the hope that by building South Africa's confidence and by recognizing its legitimate security concerns, it will obtain Pretoria's cooperation on a Namibian settlement.

But those security concerns are not simple or easy to cope with. Even if its preoccupation with the Cubans in Angola are disposed of, there remains the issue of the kind of government Pretoria will accept in Namibia. Conservative whites in both Namibia and South Africa continue to have objections to rule by SWAPO.

South African actions to date indicate small likelihood of compromise if the choice is between its security concerns and Washington's good graces.