"Afghanistanism " is a word sometimes used to designate an excessive interest in exotic places remote from American interest. But the real Afghanistan is a place of very great American interest, moral and strategic. This is so because of the epic struggle the Afghan people have been waging against the Soviet invasion of their country for more than five years -- the Kremlin now has been fighting Afghans longer than it fought Germans in World War II.

The Soviet Union, naturally, prefers to conduct its depredations quietly and in the dark. To avoid having to cope with an international public stirred by pictures of war on television, it has made a strenuous effort to keep independent observers from viewing its Afghan campaign. But some observers do penetrate, and the millions of refugees -- as much as a third of the Afghan population has been forced into foreign exile -- also provide information. The latter sources enabled a law professor from neutral Austria, Felix Ermacora, to prepare what the U.S. delegate calls an unprecedentedly "full and fair" report on Soviet conduct to the United Nations Commission on Human Rights in Geneva.

The new report accuses "foreign" troops -- they can only be Soviet -- of bombing villages, massacring villagers and summarily executing guerrillas. It lists instances in which 100 or more civilians at a time were murdered. It documents some of the specific actions by which the Soviet forces have evidently attempted to destroy the food-producing and irrigation systems so that there would no longer be a viable countryside: a policy of drying up the sea in which the guerrilla fish swim.

Mr. Ermacora's findings are sure to reinforce the deep sympathy that Americans feel for the victims of Soviet imperialism in Afghanistan and the desire to do everything that prudence allows to even the odds. Fortunately, there is a broad American consensus on this score. On the crucial considerations -- the heroism and nobility of the Afghan resistance, the absolute wrongness of the Soviet invasion -- there is little of the sort of wearing debate that marks the American attitude to, say, Nicaragua. The Afghan people are fighting a clear-cut unadulterated foreign aggression. Americans are, without argument, helping out.

What will make Moscow desist from its aggression in Afghanistan? Its casualties and economic costs go on. It continues to pay heavy political costs for despoiling an Islamic, Third World country. Fair, internationally supported terms for a negotiated solution remain available: withdrawal of Soviet troops, a return of refugees, self-determination, nonalignment. But first the Soviet Union must call it quits to its campaign to conquer Afghanistan, depopulate the country and reduce it to the status of a satellite state.