Of the four big Arab-Israeli wars, the one in 1967, whose 25th anniversary fell this week, is the most haunting. Certainly the wars of 1948, 1956 and 1973 were planned and in that sense unavoidable. But 1967, when Egypt threatened Israel and Israel ended up winning and occupying Egypt's Sinai, Syria's Golan plus the West Bank? Was that war "necessary"? Could it have been prevented? Did the United States fall down?

If you consider the conflicting passions, claims and rights of Arabs and Israelis to be endowed by history or justice, then you will shrug wearily and accept this war and the others as the destiny of the Middle East.

You will come out in the same place if you believe that the Arab world or the Arab mind is implacably hostile to the idea of a Jewish state or, contrarily, that Israel is irredeemably alien and expansionist.

There is no doubt that such mind-sets made a difference in 1967. In particular, Arab hostility to Israel provided the general impetus -- the entirely false Soviet report that Israel was massing troops to strike Syria provided the specific impetus -- for Egyptian President Gamal Abdel Nasser's fateful decision to order United Nations peacekeepers out of Sinai, where they had been lodged since the 1956 Suez war. This single, wildly irresponsible act converted a slow-burning but manageable regional confrontation into a fast-burning international emergency.

Still, I would argue, there was nothing irreversible about the sequence of events that led that fast-burning fuse to explode. I say this after sampling an Arab-Israeli-American conference on the war sponsored last week by the State Department and the Middle East Institute and reading a definitive study of President Lyndon Johnson's role by William Quandt, a Brookings specialist and conference participant.

Their shock and humiliation led Arabs to launch the notion of an American-Israeli "conspiracy" even while the six-day war of 1967 raged. That the 1956 war had most assuredly involved a conspiracy (of Britain, France and Israel) made a repetition at least conceivable. But to this day, no positive evidence of a new conspiracy has emerged -- none. Something more serious has come out instead: evidence of the subtle interweaving of Israeli and American policy strands. Quandt spins the tale in "Lyndon Johnson and the June 1967 War: What Color Was the Light?" (Middle East Journal, spring 1992.)

In its own more or less official view, he writes, the Johnson administration, bogged down in Vietnam, was caught by surprise in the Mideast. It lost control, but still consistently told Israel not to resort to force: the "red light."

Those Arabs and Americans who detected an Israeli-American conspiracy claimed Washington had in various ways given Israel a "green light" for its attack of June 5.

Rejecting both views, Quandt shows how Johnson's position shifted as the crisis tightened. He started out flashing a red light. But he switched. Prevented by Vietnam-born constraints from taking unilateral action to break Nasser's blockade of Israeli shipping at the Strait of Tiran, he came to see that there also would be no multilateral action. This led him to accept the burden of Eisenhower's 1957 commitment to Israel granting Israelis a right to act with force if the strait were closed. He passed on to an anxious Israel the word that he would not do what Ike had done in 1957 -- force Israel out of captured Arab land before it could bargain for peace. With this "yellow -- but not quite green" light, Israel went to war.

In sum, Nasser's faults of policy and perception were grievous. Egypt didn't want war, and guaranteed war.

Johnson didn't collude with Israel. He genuinely wanted to prevent a war. But his one way of doing so, once the U.N. backed away from challenging Nasser's closure of Israeli shipping, was to order up the U.S. Navy, and the Vietnam War had cost him that option. The necessary and, I would say, honorable alternative was to let Israel go it alone.

Israel has ever been at pains to demonstrate that it joined the battle only after all serious diplomatic options had been exhausted. Any hint that its war gains were ill-gotten was bound to undercut efforts either to bargain with captured territory or to retain it. It is possible to believe that the Israelis were ready for an occasion to bash Nasser, without thinking that they meant to bash him from the start.

Twenty-five years later, nonetheless, Israel is still in default on its momentous implicit bargain with Lyndon Johnson. He allowed Israel to acquire territory for a purpose -- bargaining for peace. On the West Bank, that purpose remains to be met.