YOU REMEMBER Yemen, North Yemen, "our Yemen" -- as distinguished from Marxist, Soviet-supported South Yemen, "their Yemen"? Just last March when a cry was raised that the South was invading the North, the United States rushed nearly half a billion dollars' worth of arms to the North, mainly to show Saudi Arabia that Americans are still capable of moving to reassure their Persian Gulf friends. Well, the sands are swirling a bit on the Arabian peninsula, where both Yemens strategically sit. The North's president, having pocketed the American arms, is now taking on even larger doses of Soviet arms, and advisers. Even those who claim to comprehend the tribalism that energizes politics in those parts are said to be startled by the boldness of this worthy's two-facedness. He is also described as a "gun nut," for what that's worth.

This development is no small embarrassment for Washington. The administration perhaps thought it was buying a Yemen. It turns out it may have been only renting a Yemen, for an uncertain time. This gives a certain retroactive vindication to those who said last March that the United States didn't know what it was jumping into. It puts a sour cast on the American effort to compete seriously in the Gulf region with a seemingly sure and purposeful soviet penetration that in barely a year's time has seen Soviet friendship treaties with South Yemen, Ethiopia and Afghanistan, and a steady progression of arms deals, advisers, visits and so forth, not to speak of diplomatic feelers to the Saudis.

We offer, however, another view. The arms package the United States offered North Yemen last March served a useful purpose then. It should never have been taken as the last word. It is irritating to find out so soon that in "drawing a line" against Soviet expansion in North Yemen, the United States was writing on sand. But that is probably a good lesson for the United States to absorb if it is to stay in the game for the long haul, as its need for oil and friends dictates it must. Anyway, it is not so much Americans who should fret over North Yemen's turnabout as the Saudis, who ought to know the place a lot better. And if North Yemen is not the sturdiest outpost of anti-communism, then the United States is doing plenty else in the region: military, political and economic links with other states, a growing naval presence, planning a "quick deployment force," etc.

Are the Soviets now ahead in North Yemen? Lots of luck, comrades.