As the nation braced yesterday for possible war, President Bush was described by friends and aides as unwavering in his resolve to implement a decision that he really made more than five months ago -- that the United States would take the lead in driving Iraqi forces out of Kuwait, if not by the threat of war, then by war itself.

"Given who George Bush is," said a close aide, "he made the intellectual decision quite easily that this was something worth going to war over. This week the abstract of August turned into the reality of January, but there always was an inevitability about this."

In recent days Bush has looked tired and preoccupied in his public appearances after having long seemed unaffected -- publicly at least -- by the gulf crisis.

But a senior official and longtime Bush aide noted, "I think he has been prepared since he sent the first huge contingent there in August . . . for war. . . . The tension is actually a little less now than it was the first few days" after that initial decision because "we were all petrified, the president included, that {Iraqi President} Saddam {Hussein} would attack before we were ready." The official added, "We're ready now, so that worry is off the list."

The image of Bush compiling a mental list of diplomatic and political moves and then crossing them off one by one is offered by several aides in describing the president's approach to the crisis over the past five months.

Bush, aides suggested, was more impatient than virtually anyone else in the administration about bringing the crisis to a head. After deciding to push for sanctions against Iraq and successfully assembling the international coalition necessary to put them in place, he turned to aides and asked, "What next?" one of his senior advisers said. From the outset, said this aide, the president "was very much of the notion that we could not assume that time was on our side."

Early last fall, according to his aides, Bush concluded that "the only thing Saddam understands is force or the credible threat of force," a decision that set in motion the effort to produce the United Nations resolution authorizing the use of force unless Iraq withdrew from Kuwait by last night's deadline.

"If there were no deadline, the threat of force was toothless. We would be forever caught in the cycle of the past two weeks, a diplomatic initiative a minute, a final 'last best hope' leading to another final 'last best hope.' There had to be an end to it," said one official.

Bush thought the deadline strategy would work against Saddam. "My gut says he will get out of there," Bush said in a Time magazine interview published recently. Now, aides said yesterday, Bush "feels in his heart" that every diplomatic approach to avoiding war has been tried. Said one official, "If the French and the Arabs and {U.N. Secretary General Javier} Perez de Cuellar and the Yemenis and the Algerians and dozens of others haven't done it, what will? If there was some magic way out of this out there, don't you think someone would have come up with it by now?"

White House Chief of Staff John H. Sununu, in an interview at Christmastime, said that Bush was managing the pressures of the crisis by assuring himself he was not missing some unexplored road. "I think he has worked this thing and wrung it out to such detail that he's quite comfortable with where he has ended up," Sununu said.

Bush himself has suggested over the long months of the gulf standoff that he saw his management of it as a series of small and large problems to be disposed of one by one. The holding of Americans in Kuwait -- particularly those in the U.S. Embassy, a potent symbol to Bush -- was one of the president's deepest worries, his aides said this week.

House Majority Leader Richard A. Gephardt (D-Mo.) recalls Bush being "visceral" in his anger that diplomats were again being held hostage by a tyrant, a situation Bush repeatedly cited as a disgrace during his unsuccessful campaign for president in 1980.

When Saddam let the Americans go, an official said, it lifted a major burden. "That's one less thing I have to worry about," Bush said at the time.

At least until last weekend Bush demonstrated his vaunted ability to compartmentalize his life, to put aside a problem and throw himself into something else.

On the day last week when the talks in Geneva between Secretary of State James A. Baker III and Iraqi Foreign Minister Tariq Aziz ended in failure, Bush managed to hold some political meetings and later to hastily organize a dinner at a local Chinese restaurant to decompress. Even last weekend, friends said, he was able to enjoy sledding and other sports at Camp David.

Over the past two weeks, old friends report getting the personal Bush notes and letters that have been a lifelong habit of his. One friend who got a call said Bush was "the same old George," gleefully immersed in the day's politics and news of old friends.

A friend who dined with Bush recently described him as "healthy of mind and spirit" and looking "a lot better after a drink" than at his recent news conference. "I think he has made the decision to go to war. I'm very sure of it. He's not happy about it but he's at peace with it."

A senior official, offering a broad assessment of the turning points of the crisis, said the "fundamental decision" was that military force would be sent to Saudi Arabia, that force would be "big time or nothing," and that if it came down to it, the military option would be used. That, the official said, was the "cosmic" decision from which all others flowed and from which Bush has never wavered.

Rep. Jim Leach (R-Iowa), a friend of Bush's for two decades who has had several conversations with him since August, said that "never in my memory" has Bush been "more thoroughly consistent and more thoroughly resolved" from the outset on how an issue should be handled.

Interviews with some of those who have tried to talk to Bush about the horrors of war suggest that the president, while not disregarding them, had determined the "immorality" of not forcing the issue with Iraq was worse than the implications of doing so with force. When Episcopal Bishop Edmond L. Browning met with Bush in December and urged him to try to provide moral leadership for the world by finding a peaceful way out of the crisis, Bush responded, "How can we morally not do anything?"

When his aides and associates describe the gulf crisis in terms of "who George Bush is," they cite not only the first major event that molded his view of the United States' role in the world, World War II, but also the Vietnam War.

Serving in the "good war" at age 18 and watching a presidency destroyed by another war more than two decades later, associates say, defined Bush's sense of when war is justified and how it should be waged.

In his autobiography, Bush makes both these wars central in his life. On Vietnam, he recalls passing up the inauguration of Richard M. Nixon to travel to Andrews Air Force Base, the only elected Republican there, to witness the poignant scene of Lyndon B. Johnson, his presidency destroyed, leaving Washington. His handling of the war, Bush wrote, sent Johnson back to Texas "a defeated man."

In the same book, Bush recounts the now familiar story of hearing Franklin D. Roosevelt's secretary of war, Henry L. Stimson, urging members of his prep school graduating class in 1942 to continue their education. Bush, 17 then, ignored the advice, certain of the need to fight Adolf Hitler and enlisted to become the Navy's youngest aviator.

That war, Bush would say in a 1988 foreign policy address, set the stage for America to "fulfill its historic mission. We defeated the Nazi tyranny and from the rubble of a war built a new international order."

The concept of the need for a "new international order" helped into place by the United States to replace the vanished rules of the Cold War era is today one of the fundamental reasons Bush offers for why the United States must take the lead in ejecting Saddam from Kuwait. Although he cannot define this new international code of conduct, "Bush thinks there are rules by which civilized nations exist, or at least there ought to be," according to an associate.

The presidential campaign that brought Bush to the White House focused on how the next president would manage peace, not war.

"The Soviets are withdrawing from Afghanistan," he said in the fall of 1988. "The Vietnamese are beginning to leave Cambodia. The Cubans are negotiating to leave Angola. Peace is breaking out all over."