If you want to know whether war with Iraq is inevitable, don't turn to the latest policy pronouncements from the White House. Dive into the debates that took place in the Oval Office the last time a U.S. president was confronted by what he considered to be an existential national security threat.

Seeking insight into the Bush administration's discussions about Iraq, I have become engrossed by the transcripts of tape-recorded conversations between President John F. Kennedy and his advisers as they argued about how to respond to the deployment of Soviet nuclear missiles in Cuba. The transcripts are the closest most of us will get to being a fly on the wall of the Oval Office at a moment of great national drama. If you close your eyes, the voices of Robert McNamara, Dean Rusk and McGeorge Bundy recede into history, and are replaced by those of Donald Rumsfeld, Colin Powell and Condoleezza Rice.

I do not mean to suggest that the war on terrorism is a replay of the Cuban missile crisis, still less that GWB is a reincarnation of JFK. But there are parallels. In 1962, Kennedy decided that the presence of Soviet missiles in Cuba was an intolerable threat to the nation's security; Bush feels much the same about the spread of weapons of mass destruction. There are also differences. Saddam Hussein is at once less threatening and more menacing than Soviet leader Nikita Khrushchev. Measured in missiles and nuclear warheads, the Iraqi military threat cannot be compared to the Soviet military threat. Nevertheless, the administration has a good case that a potential alliance between terrorists and rogue states poses the most serious long-term menace to the United States.

The missile-crisis precedent has been on the minds of Bush foreign policy intimates as they prepare for war with Iraq. National security adviser Rice has discussed the parallels between Iraq and Cuba with a former academic colleague, Philip Zelikow, who is co-editor of the "The Kennedy Tapes: Inside the White House During the Cuban Missile Crisis." Bush's advisers are not averse to comparing their man to Kennedy, despite their differing ideologies. After all, even though Kennedy never bombed Cuba, his "eyeball-to-eyeball" tactics did succeed in getting Khrushchev to back down without plunging the world into nuclear war. We still don't know how the Iraq crisis will play out.

Until the archives of the Bush presidency open up three decades or so from now, we are unlikely to get a full and objective picture of the debates now unfolding in the Oval Office. In the meantime, the Kennedy transcripts provide invaluable insights into the actions of a modern-day president confronted by a huge international crisis:

* Presidents change their minds. Government spokesmen hate to admit that U.S. foreign policy ever changes or that presidents think better of decisions they made a month earlier, or even yesterday. In reality, policy is constantly evolving, as part of a never-ending process of argument, trial and error, and ideology colliding with the real world. In 1962, Kennedy was clear about what he wanted to achieve: getting Soviet missiles out of Cuba. But his tactics changed from day to day, in response to world events, the arguments of his advisers and his political instincts. To take just one example: He started off assuming that it would be necessary to bomb the missile silos; he ended up resolving the crisis through a blockade and back-channel talks with Khrushchev.

In the case of Iraq, Bush seems equally firm about the need to disarm Hussein, although he has wavered on the related question of "regime change." Exactly how he will achieve this goal remains uncertain. Unlike others in the media, I tend to believe repeated White House claims that the president has still "not made up his mind" about going to war to rid Iraq of its weapons of mass destruction. It is still unclear how much time Bush is prepared to give to U.N. weapons inspectors. Perhaps even the president does not know the answer to that question.

* Presidents have a broader field of vision than their advisers. Kennedy's advisers viewed the missile crisis from their own vantage points. Air Force chief of staff Curtis LeMay advocated massive airstrikes; when he did not get his way, he accused Kennedy of "chickening out." While Gen. LeMay saw the confrontation in strictly military terms, Kennedy considered a vast array of factors, from the reaction of U.S. allies to the effect on other global flash points to winning the battle for public opinion, both at home and abroad. In his mind, everything was connected. A U.S. attack on Cuba could provoke a Soviet attack on West Berlin. In order to pressure Khrushchev into pulling out his missiles, he needed international backing.

In his gut, Bush may side with Defense Secretary Rumsfeld and the Pentagon hawks in their arguments about the need for regime change in Iraq, even at the price of going to war unilaterally. But the very fact that he is president means he must be attuned to a wide variety of other circumstances, including the views of the American people. Polls show that Americans are generally supportive of a war with Iraq endorsed by the U.N. Security Council, but are skeptical of going it alone.

While Bush has inherited the mantle of commander in chief, he has much less relevant experience to use in forming independent judgments than Kennedy did. Kennedy lived in England with his parents during the runup to World War II; he commanded a patrol boat during the war and later wrote books on leadership and appeasement. Bush may be tough-minded, but the jury is still out on his sense of history.

* Public presentation of policy is key. At one point in "The Kennedy Tapes," the president berates State Department spokesman Lincoln White for getting slightly ahead of him in threatening military action against Cuba. Like the Kennedy White House, the Bush administration devotes enormous effort to managing public expectations. The recent confusion over the timetable for an attack on Iraq is an example of what happens when a public relations machine that prides itself on discipline sends out conflicting messages. In order to reassure jittery allies, Bush needs to appear reasonable and flexible. When he wants to convince Hussein that the time for prevarication is over, he becomes impatient and inflexible. He knows that the Iraqi leader has little incentive to make concessions as long he perceives that he still has some wiggle room.

* Allies matter. There is a huge difference between fighting a war with allies and fighting a war without them. Despite the Bush administration's reputation for unilateralism, the president is influenced by the actions and opinions of America's friends, particularly the British. Prime Minister Tony Blair has given Bush unstinting public support over Iraq. In return, he is asking that Bush allow the U.N. weapons inspections process to play itself out. The Bush-Blair relationship is reminiscent of the relationship between Kennedy and then-Prime Minister Harold Macmillan during the Cuban crisis. In public, Macmillan was Kennedy's number one international cheerleader. In private, he was a leading voice of caution.

* What the other side does also matters. Like Kennedy before him, Bush is engaged in a high-stakes game of poker, not solitaire. He must respond to the play of his opponent. Hussein's options may be limited, but there are things he can do that will help determine Bush's choices. The most obvious is for him to acknowledge -- at the last possible moment -- that he still has some Scud missiles and chemical weapons tucked away in an attic and is willing to give them up. Such a "deathbed conversion" would pose a tricky problem for Bush. The doves, both at home and abroad, would likely seize on any disarmament move by Hussein as an excuse for avoiding military action. It would be difficult to demonstrate that Hussein has other weapons of mass destruction that he is continuing to conceal.

The Cuban missile crisis suggests there are limits to the length of time the Iraqi crisis will be allowed to play out. Like Kennedy, Bush has to sustain a sense of momentum by gradually escalating the pressure on Hussein to a point of climatic confrontation. It is difficult to predict exactly when this moment will come. But just as Kennedy feared that U.S. threats would become hollow if too much time elapsed before Soviet missiles were withdrawn from Cuba, Bush must also be concerned that American credibility will be undermined if the U.N. weapons inspection process drags on too long.

* Presidents (and their advisers) are human beings. They may be more driven and disciplined than the rest of us, but they, too, have strengths and weaknesses, passions and foibles. Sometimes they are bold and visionary, at other times surprisingly inarticulate. Only now are we discovering the extent of the strain that Kennedy was under at the time of the Cuban missile crisis. Medical records obtained by a biographer, Robert Dallek, show that at the same time Kennedy was firing off messages to Khrushchev, he was in excruciating pain from a variety of ailments, including Addison's disease, and was swallowing a variety of drugs including two different hormones.

The human side of presidents -- which comes across with great clarity in "The Kennedy Tapes" -- is both troubling and reassuring. Troubling because presidents, too, make mistakes, and one false move can lead to catastrophe. Reassuring because history suggests that presidents and their advisers are generally sane, well-meaning people, struggling to do their best in sometimes impossible situations, with a healthy instinct for America's best interests and the survival of the human race.

The war on terrorism offers challenges and dilemmas different from those faced by Kennedy, and it is still too early to say whether the hawks or doves are right. If a U.S. invasion of Iraq is followed by the release of biological weapons in New York's or Washington's subway, one nightmare scenario, many Americans might question Bush's judgment. If, on the other hand, the price of inaction is the supply of weapons of mass destruction to terrorist groups, as the administration contends, then the cost in lives and resources of a second Persian Gulf war will be justified.

It is an agonizing choice for any human being to have to make. Michael Dobbs covers foreign policy for The Post. He is the author of "Down With Big Brother: The Fall of the Soviet Empire" (Knopf).

President John F. Kennedy with ExComm members of the National Security Council in 1962.