Sometimes in Russia I think a drain will stop and the whole system will fall apart. But though everything is always going wrong, the collapse doesn't come.

Consider the leaders, for instance. Obviously they are old and fragile. Alexei Kosygin has just died. Leonid Brezhnev, 74 on Friday, walks stiffly and sometimes seems not to know where he is. Even when everybody around him is smiling, his face is frozen.

But when I was here 18 months ago, Brezhnev looked absolutely ghastly. When the two men appeared at a meeting of the Supreme Soviet, Brezhnev seemed more sickly than Kosygin. Clearly he has recovered some, and the Moscow gossips talk of a miraculous cure.

Consider, second, the economy. All over Moscow these days, there are long lines outside the food stores. In some quarters of the city, flour and potatoes are in short supply. The countryside is worse, and bitter jokes about the scarcities go the rounds. "Can America become a socialist country?" one gag asks. "Sure," the answer goes. "But then where would Russia buy grain?"

Food apart, consumer goods seem more abundant than before. Clothing is plentiful, and the only lines are for expensive items. The steady increase in the number of private cars continues. Indeed, because of the cars, snow removal has been a problem in Moscow this year.

Despite these discontents, the dissident movement has been absolutely shattered. Its best-known leaders are either abroad, as in the case of Alexander Solzhenitsyn, or in internal exile, as in the case of Andrei Sakharov. When the annual celebration of international Human Rights Day was held in Pushkin Square a fortnight ago, only 10 persons showed.

But while everything else in the Soviet Union has its ups and downs, there is a Russian constant. The development of military might goes on apace. Russian forces are in Afghanistan, along the borders of China and Iran, and all around Poland.

Defense Minister Dimitri Ustinov has recently been especially assertive. He sounded off against the Poles during a meeting of the Warsaw Pact leaders here in Moscow on Dec. 5 and 6. On Dec. 10, at a meeting of officers in the Moscow military district, he reasserted Russia's paramount commitment. He claimed that during the past five years "the defense capacity and combat readiness of the Soviet Army and Navy have attained a new level of quality." He said the Communist Party was "permanently pledged to reinforce the defensive capacity of the country."

In keeping with that promise, the defense buildup goes on. Conscripts due to be released in the fall have been retained in the services. The deployment of the SS20 missiles targeted on Western Europe continues. A rumor here is that if the United States does not accede to the SALT II treaty in the next six months, Russia will step up production of the SS18, the giant multiheaded missile that presents the main threat to the American nuclear deterrent.

None of this means that the Russians are 10 feet tall. Nor that they plan to attack the United States, or move on Poland or Iran. What it does mean is that the Russians know how to live within their contradictions. The manifold weaknesses of Soviet society are not going to prohibit the steady growth of Soviet military power.

So the Western allies, and especially the United States, have to develop a long-term strategy for dealing with that power. Arms control certainly has a place in that strategy. It is evident that the Russians want to go ahead with the SALT II treaty in some form. They are holding the door open for the Reagan administration. Accepting the Soviet overture makes sense, for the treaty is in the American strategic interest.

But, of course, the United States has to do much more. It needs to strengthen forces on the ground in areas where the Soviets now possess superiority -- notably in the Persian Gulf areas. It has to develop a large pool of trained military manpower -- presumably by enactment of a new draft. It has to protect the strategic deterrent.

For the basic fact is that power is the name of the Russian game. To take comfort from Soviet internal weaknesses is to be assured of a nasty surprise. The United States has to drop once and for all the illusion that the Russians will cease to go for military strength, that they will allow their power to mellow, that they will beat themselves.