THE RUSSIANS are arming for war; NATO is asleep.

Unless the allies start taking war seriously and following the advice of their generals, disaster will occur. The Russians will exploit their advantages either politically or by launching World War III.

This is the message of The Third World War: August 1985 , which no one not desperate for a label would call a "novel." It is a "report" drafted by a group of British generals soon after the end of that conflict. There is no plot, no character development, indeed hardly any people at all.

The authors have done an amazing job of sticking to the ground rules that they must have laid out for themselves. Except for the copyright date and two pages of acknowledgements, there is nothing in the book to indicate that it was not written in 1987. Activities up until 1977 are presented as they actually occurred. From then on the authors were free to have things happen as they chose and, except for the events that they needed to manipulate to bring on the war, their predictions are unexceptional. The Shah of Iran, for one, may be pleased to know that he remains in power throughout the book.

Although military historians, weary of refighting the battles of World Wars I and II, will welcome a new set of military encounters to analyze, this is not the point of the book. General Sir John Hackett and the other authors have a serious and specific message which, as the book proceeds, they repeat over and over as if aware that it could easily be lost in the fascination with the detail of the war.

"If the crisis of 1985 had occurred in 1977, say, or even in 1978, it is, as we have seen, scarcely conceivable that the Soviet plan for an advance to the Rhine, the dismenberment of the Alliance and the total destruction of the Federal Republic of Germany could have failed given the state of preparedness of the Allies at that time.

"What was done in the years between 1978 and 1984 was enough to prevent this."

This is the kind of warning that NATO generals and their civilian supporters have been giving us for 30 years. The Third World War is another effort to persuade.

Its authors have three very difficult tasks. They must somehow start a large war in Europe. They must have both sides fight in such a way that the improvements they advocate in NATO forces can make a difference. Finally they must have the war end on terms favorable to the West. (Text omitted)

All of this they do -- it is impossible to fail in this contest if you control the typewriter. However, the implausibility of their scenario at every step serves only to undercut their argument and to support the position of those who have suggested that the center of Europe is the least likely place for war to break out and that the military balance which now exists is sufficient.

Consider how the war starts. The Kremlin reacts to unrest in Poland -- caused by the election of an American president who campaigned with hints of a rollback in Europe -- by launching a worldwide political offensive designed to humiliate the new American leader.This involves stirring up the pot with aggressive activity simultancously in the Middle East, India, central America and southern Africa. These operations have the modest success of all such efforts to influence local events. But somehow their failure to have greater results produces such concern in Moscow that "the rapid use of the remaining real Soviet assets in the shape of its truly formidable conventional attack capability in Europe." And so the Russians enter Yugoslavia, the Americans intervene to defend the Balkan state, and the Russians invade Germany.

There -- World War III is underway. The fighting itself involves an equally breath-taking belief that both sides will behave not with the caution of the past but rather to prove the authors' point. The Russians fight a conventional war and stop their advance just before the NATO countries would run out of ammunition. They drop a nuclear weapon on Birmingham, see Minsk destroyed in return, withdraw, and the Soviet empire falls apart.

There may be a case for the three percent increase in real spending for NATO to which the United States and its allies have committed themselves, but it cannot be found in The Third World War . In fact the reverse might be true. The Central Front remained quiet for some 30 years until we started taking the advice of the generals. CAPTION: Map, Projected Soviet offensive, summer of 1985 (from "The Third World War")