The Belgians, NATO members, had promised to do their alliance duty by starting to deploy their share of new missiles this month, and they have now delivered on their promise. It was not easy politically for Prime Minister Wilfried Martens but, facing elections at the end of the year, he decided to take the step well in advance and to take it in style. So he did. His announcement came last Friday, and over the weekend the first batch of 16 cruise missiles were flown in. The 16, and the 32 due to come later, will not make the difference between security and no security for Belgium and Europe. But by deploying them, Belgium gives West Germany, the crucial frontline country, crucial political company. That is what alliance solidarity is about.

The Soviets, not by design, gave the Belgians some useful help at the end. At the Chernenko funeral, the Belgian foreign minister asked his Soviet counterpart a question that, one can safely guess, he knew how the Soviet would answer. Will you unlink talks on offensive weapons from talks on defensive weapons? the Belgian asked. Linking them is, of course, the essence of the Soviet negotiating strategy. The Belgian government was then in a position to inform its closely divided electorate that, since Moscow had left so little room for negotiations on offensive arms, Belgium had no honorable or reasonable choice but to start deploying. Any other response would have given Moscow an unremunerated political and psychological boost just as the Geneva talks were getting under way.

Sixteen cruise missiles: that's not very many. The Soviet Union has deployed a larger number of SS20s -- 18 -- just in the last two months. The total number of triple-warhead, first-strike SS20s trained on Europe has now climbed to 414. For more than five years Moscow has been putting Western Europe under the gun, literally. NATO started answering the Soviet deployments only last year. The governments of West Germany, Britain, Italy and Belgium have come forward, all of them at considerable political cost, but all of them finally convinced that deployment was essential in order to maintain the essential alliance qualities of combined strength and mutual obligation. Only the Dutch still lag.