IN ALMOST every international crisis where force is threatened, there comes a teeter point, a moment when the situation looks menacing but still may be saved. The parties inevitably know this and play their strategies accordingly. The trick is to go right up to but not over what John Foster Dulles termed, aptly, the brink. If the result is attained without the actual use of force, it is called a political solution; if not, it is called a war.

So it was in the Falklands crisis in the spring of 1982. Argentina had seized the British-claimed islands, but a resolution without the further direct application of force still seemed possible. Though a British task force had arrived on the scene to bring pressure to bear, various diplomatic initiatives, including Secretary of State Alexander Haig's shuttle and an effort by Peru, were in the works.

But then the British sank the Argentine cruiser General Belgrano, with the loss of 368 lives. Diplomacy was overtaken. War determined the outcome.

The sinking of the Belgrano has been a matter of contention since the war, but recently the controversy has taken on fresh intensity. Newly leaked documents of the what-did-she-know-and-when- did-she-know-it kind suggest -- suggest to some, that is; they do not prove -- some shocking things about the policy of Margaret Thatcher's Conservative government: that the Belgrano was attacked despite advice that an attack would violate international law; that the ship, far from being the threat to the fleet that the government claimed, was steaming away from the fleet and was in any event outside the 200-mile exclusionary circle the British had drawn around the Falklands, and that Mrs. Thatcher ordered the fleet to attack precisely in order to spoil the diplomacy then under way -- she wanted war.

(We should add here that a further allegation in the new package -- an allegation we find impossible to credit -- is that Britain contemplated a nuclear attack on an Argentine city.)

Historians might say that the Belgrano question is of the sort best left to historians for definitive answer. But the question is being hotly, and necessarily, debated in Britain now. Mrs. Thatcher is being accused in the press of an unspeakable offense -- choosing war over peace and, then and now, trying to cover it up -- and the matter will likely move to Parliament in the fall.

The gravity of these charges means they cannot be left hanging. In the nuclear age, especially, nothing is more important than the matter of how countries in disputes go up to, and sometimes past, the teeter point. Everything depends on it.