When a Soviet soldier tried to defect in Afghanistan the other day, our embassy there was for understandable reasons, in something of a flutter. Diplomacy and superpower politics aside, the problem was that no one in the embassy spoke Russian. Consider that fact: one hundred thousand Soviet troops and thousands more Soviet advisers enmeshed in a nasty war that has seriously damaged U.s.-Soviet relations. And, apparently, not a single American official capable of interviewing an ordinary Russian dogface.

American preparedness is a major issue in this presidential campaign season, and much has been said about our military posture. But what about our ability in sensitive far-flung posts to communicate with the army of our Soviet adversaries? Suppose a division of the formidable Red Army had had enough of Afghanistan and contacted the embassy in Kabul to let us know. We wouldn't even have been able to take the call!

The official explanation for the lapse is that there are less than 20 people in the embassy, including six Marines; and with everything else that needed to be done, speaking Russian, well, just fell between the cracks.

If the situation in Afghanistan were unique, it would be merely embarrassing. But the reality is that Americans too often are incapable of carrying out their functions abroad because of language shortcomings. The consequences range from the comic to the tragic. Remember the American translator in Poland a couple of years ago who fouled up a presidential greeting to the point that American jokes became the rage in Warsaw?

One of the worst cases was in Cambodia a decade ago, where a major U.S. military and diplomatic commitment was undermined in large part because we so utterly lacked any sense of understanding about the country. At times there were no more than one or two Khmer-speakers in the entire American establishment. French and later some English were the lingua franca for dealing with most Cambodians, which explains why we were shut off from the vast majority of the country's people.

The problem extends to private Americans as well. In 1976, when the networks were vying with each other to win the lucrative contract to broadcast the Moscow Olympics, they relied on Soviet-supplied interpreters during the bargaining. Turning matters around, it would be unthinkable for the Soviets to depend on Americans in a complex technical negotiation. Now, we may well think the Russians are excessively suspicious. But when it comes to doing business -- any business -- the idea that you rely on the other fellow's agent to tell you what is being said seems absurd.

Given the current hand-wringing on America's trade weaknesses, some figures compiled by Sen. S. I. Hayakawa (R-Calif.) are also revealing. There are, The New Republic quoted him as saying last spring, 10,000 Japanese businessmen in the United States, all of whom speak English, but only 1,000 U.S. businessmen in Japan, only a few of whom can speak any Japanese at all. The savviest traders are the ones who can chat up the customer.

But mercenary considerations aside, the Afghanistan incident reflects a serious continuing problem for U.S. diplomacy. At the present time, for instance, there are no Somali-speakers among the officials at the U.S. Embassy in Mogadishu, according to State Department officials. This is bound to complicate matters at a time when the United States is engaged in sensitive discussions about the implementation of a new Somali-American basing agreement.

At the height of the Iranian revolution in 1978, according to The New Republic article by Executive Editor Morton Kondracke, only six of the 60 U.S. Foreign Service officers there were "minimally proficient" in Farsi. At the time of the takeover of our embassy last November, congressional sources say, even fewer of our envoys could make themselves understood in the language of their captors.

It would seem difficult to defend a policy of not speaking the language of the country to which you are assigned. But some officals make the point that it is too much trouble to learn the obscure languages of many lands. Take Somalia. Everybody who counts speaks English, said one U.S. diplomat. "Only the people out in the countryside speak Somali," he said.The attitude is the same one that prevailed in Cambodia.

As for not speaking Russian in Afghanistan, the reasoning behind the State Department policy is that Americans are "supposed to have as little contact with the Russians as possible," one diplomat explained. So to deal with the hapless would-be defector, a U.S. official had to be flown from Moscow to talk to him. Shortly after he arrived, the defector met with the Soviet ambassador in Kabul and said all things considered, he'd rather go home.