War, it seems, is on everybody's mind these days. City councils and state legislatures race to align themselves with the nuclear freeze movement. The Pentagon rushes to attain ''maritime superiority'' and says it must be prepared to fight a protracted nuclear war.
Even Soviet dissident Andrei Sakharov said recently, ''It is necessary to restore parity in the field of conventional weapons. . . . Both sides have to be confident of their security without relying on atomic and thermonuclear weapons.''
This is exactly the point made in Gen. Sir John Hackett's new book, ''The Third World War: The Untold Story.'' A sequel (or perhaps update) of his 1979 bestseller, ''The Third World War: August 1985,'' this ''cautionary tale,'' as he calls it, should join Jonathan Schell's ''The Fate of the Earth'' as essential reading for those who want to go beyond a bumper-sticker understanding of what a future war would be like.
It is not easy reading, however. Full of military jargon, acronyms, strategy, and tactics, it falls somewhere between being a gripping war story and a handbook for NATO planners or war college students. A reader looking for one or the other will not be wholly satisfied.
We are given brief glimpses of interesting and attractive characters - Andrei Nekrassov, a young Soviet Army officer, for example - but none of these are developed as were the combat opponents in, say, ''The Young Lions.''
But this is not intended to be ''The Red Badge of Courage'' or ''From Here to Eternity.'' It's a message with a medium that one would expect from a World War II hero and former commander of the British Army of the Rhine.
As did Sir John's earlier book, this details (as if written in 1987) the brief and violent three-week war between the Western allies and the Warsaw Pact, culminating in a limited nuclear exchange in which Birmingham, England, and Minsk, USSR, are devastated, the Soviet political structure collapses from within, and the world is left intact but with problems of greater magnitude.
Added elements include more detail on Soviet military thinking and capabilities gained from defector Viktor Suvorov, who commanded a Soviet motor rifle company in Czechoslovakia. This book also takes account of new historical developments, like the election of Ronald Reagan and the fall of the Shah of Iran.
Its main value is that it shows just how quickly geopolitics can degenerate into war if the intentions or capabilities of one's opponent in the world arena are misunderstood. Hackett argues that the way to avoid nuclear war is for the West to be so strong in conventional arms and posture that the Soviet Union would not risk a push into Western Europe. In this respect, his position is not that different from that of former US officials Robert McNamara, George Kennan, McGeorge Bundy, and Gerard Smith, who in recent months advocated a nuclear weapons no-first-use policy for the Atlantic alliance.
Some readers no doubt will bristle at Hackett's equating peace movement members with Lenin's ''useful fools.'' But if they agree that war is too important to be left to generals, then they can help prevent it by learning as much as possible about how war could well be started and fought. And a good place to begin this necessary and sobering education is with this scholarly general's new book.