The new danger in Africa, just when the Russians and the Cubans should be beginning their withdrawal from Ethiopia, is that instead of going back home they will turn around and go to the aid of the Rhodesian guerrillas. What will the West do then? Its threats have done nothing to get them out of Ethiopia. It was only when the provocation that brought them there in the first place was removed, and the Somali regular forces that had invaded Ethiopia retired in disorder to their own borders, that the prospect of a Soviet-Cuban withdrawal became at all real. There is a lesson here for the West that we will ignore only at our peril.

Somalia was the aggressor in Ethiopia, and the West found itself on the wrong side. That gave the Kremlin the opportunity to introduce its expenditionary force into Ethiopia, with the approval of most African leaders. Now a similar chain of events may be beginning in Rhodesia.

The new Rhodesian settlement negotiated by Ian Smith and the three African leaders inside the country is rejected by the guerrilla leaders now outside Rhodesia, and by most of the black African countries. The West would again find itself on the wrong side if it gave support to the Smith formula, because the "internal settlement" is a transparent device to ensure that the real decisions in Rhodesia will continue to be made by the whites.

That is what Moscow Radio has been telling the Africans, and the analysis cannot be easily controverted. It has also said, more ominously, that the new situation creates "a serious threat to peace" that could be made an excuse for the introduction of Cuban and Soviet military forces. "The leaders of the Patriotic Front," Moscow said, "have stated that they will step up their armed struggle against the illegal Smith regime and its puppets, and will struggle to a victorious conclusion." That is one threat to peace.

The other, which is really the obverse of the first, is that Rhodesian security forces will seek to preempt the stepped-up attacks by Patriotic Front guerrillas based in neighboring Mozambique and Zambia. To do so, the Rhodesian forces would have to cross international borders, as they have done repeatedly in the past, and thus give both Zambia and Mozambique a reason for requesting Soviet-Cuban military aid.

Once again, as in the case of Ethiopia, the Kremlin would be in a position to say that a communist expeditionary force had gone to Africa at the request of a legitimate government to help it against invaders - though this time the invaders would be white.

Ian Smith thinks he knows what he is doing. He believes that the West in general, and the United States in particular, cannot easily afford to allow yet another communist military intrusion into Africa. The United States has tried to prevent the communist intrusion into Angola with little more than angry words, but when those failed it warned the Kremlin that any repeat performances would have grave consequences. But when the Kremlin did repeat the performance, in Somalia, the United States was not in a position to do anything about it - unti it was too late. By the time the Somalis agreed to withdraw - partly under prompting from Washington, but also under blows from the communist expeditionary force - there were more than 10,000 Cubans in Ethiopia, a thousand Russians, two Soviet generals, and large stocks of Soviet arms.

The pattern that had so often been anticipated by students of Soviet policy in Africa was assuming an increasingly clear shape. First a testing of the waters by the Kremlin in Angola, and then a bolder venture into Ethiopia, which could become a stepping stone to Rhodesia, so that ultimately Soviet forces could intervene in South Africa when that unhappy land explodes.

The terms of the "internal settlement" and the world reaction to it would make it difficult to keep the Kremlin out if it decided to intervene again. Although the Foreign Office in London and the State Department in Washington have take refuge in ambiguity, while they try to agree on the next step, the condemnation of the Salisbury deal by Andrew Young, the U.S. ambassador to the United Nations, makes one thing clear. The Western powers will not be able to support Ian Smith in imposing on the Rhodesian blacks a settlement that ignores the Patriotic Front and its guerrillas.

The pictures of happy blacks dancing and chanting their approval of the "internal settlement" do nothing to alter the realities of the situation. True, the camera does not lie - but it is not much help in determining where the political loyalties of the population lie. Those are measured by the ballot box.

Andrew Young takes a different view of Soviet adventures in Africa from that held by Zbigniew Brzezinski, President Carter's national security adviser. Young believes that the Kremlin will not be able to build a permanent Soviet presence in Africa, that sooner or later its own blunders, and African pride, will lead to the expulsion of Soviet influence, as has happened so frequently in the past. Brzezinski, who is more concerned with the global strategic picture than with what happens just in Africa, is sometimes accused of taking unthinkingly the alarmist view of Soviet actions, which is said to come automatically to a man with his Polish American background.

But there is one important element in that background that should put him on Young's side. Anyone steeped in Polish history as he is will remember the "internal settlements" imposed by Russia on Poland during an occupation that lasted more than 100 years - and the refusal of the great majority of the population to acquiesce in them, even though the Russians usually managed to find a new Polish leaders who were prepared to act as their puppets.

The parallels with the black leaders who accepted Ian Smith's "internal settlement" may not be exact, but they are sufficiently suggestive to give pause to a man with Brzezinski's background. He certainly wants to stop Soviet incursions into Africa once and for all - but he may find that the way to do it is to give greater U.S. support to those African leaders, in Rhodesia and elsewhere, who cannot be accused of being quislings by their compatriots.

If the West allows itself to be maneuvered once again into the position of supporting the wrong side, then it will also find itself on the losing side - and the Kremlin will have made another gain in the steady unfolding of its African strategy.