President George W Bush has remained serenely calm as he made the decision to go to war, driven by an inner faith.
George W Bush: Increasing calm as the crisis has intensified
It was Harry S Truman, the only world leader ever to have ordered the use of nuclear weapons, who famously said that being the President of the United States was like riding a tiger, for it was impossible to control the violent tumble of events.
Such was the intense strain on America's 33rd president that he decided against seeking a second term.
After almost eight years of the 'buck stops here' - the famous slogan the plain-speaking mid-westerner placed on his Oval Office desk - it was time to go.
Contrast the experience of Harry S Truman, who buckled under the pressures of America's Cold War struggle, and George W Bush, who seems to relish the sharp focus and intensity of the war on terrorism.
These past few days, he has been a portrait of calm - whether addressing the nation in the red-carpeted grandeur of the Cross Hall at the White House, or playing with his dogs, Barnie and Spot, on the South Lawn outside.
And ever since it became clear that diplomacy was failing, his mood seems to have become even more relaxed.
After all, his relationship with the United Nations was always a marriage of convenience rather than a marriage of real commitment.
He seems pleased to have been freed from the constraints it imposed.
So on the brink of war, this is a president at peace with himself - a man of rigid conviction, with an abiding belief in the righteousness of his cause.
The truth is, America's 43rd president believes he is doing God's will.
Throughout the crisis, his daily routine has stayed pretty much the same.
Bed before 10PM, a 5.30AM rise.
Bible study and prayer.
At least half an hour each day of exercise - a three-mile run or a session with the weights.
Lunch in his private dining room, pouring over the sports pages and watching ESPN, the American sports channel.
While his diary has been trimmed - no public events are scheduled for the next few days - he still takes part in the customs and rituals that punctuate a president's day.
Last Friday afternoon, for example, even as the diplomatic effort was coming to a head, he found time for a brief awards ceremony in the White House.
One of the recipients was one of our BBC cameramen, Mark Rabbage, who was struck by the president's remarkable good humour and levity.
As he cracked gags about the Oval Office furniture, he seemed like a man without so much as a care in the world.
For all the president's calmness and resolve, America right now faces a moment of great uncertainty - largely because it is embarking on an historic new path.
This is the first war fought under the Bush doctrine's strategy of pre-emption - military strikes against unrealised threats.
Its long-term implications are impossible to fathom - both to America, its allies and the international order.
But its author seems to be the most confident and self-assured man in town.