Everything has changed for us all – especially for George W. Bush. When he was elected president, the country enjoyed peace and prosperity, the twin goals of every presidential candidate. He could look forward to what seemed to an endless economic boom and continued peace in the wake of a half-century of the Cold War. He thought he could count on a hefty budget surplus to pay for things like a massive tax cut and a huge visionary national missile defense system.

But suddenly the economic bubble burst, dumping the country into recession. And then, out of the blue, hijackers crashed passenger jets into the World Trade Center and the Pentagon, forcing the country into a defensive war against international terrorism. Mr. Bush found himself converted into a war president, commander in chief against a shadowy network of religious fanatics obsessed with a hatred of America and armed with a readiness to die for their cause.

As the operations in Afghanistan have progressed, President Bush has taken charge with a firm hand. He immediately assured the nation that America would fight back, while warning that the war against terrorism could mean sizable American casualties and could require many months or even years of effort. He launched a bombing campaign to control the air over Afghanistan and prepare for ground action to track down Osama bin Laden and defeat his Taliban protectors. He ordered a crackdown on al- Qaida’s sources of revenue. He organized a broad international coalition to help with the military operations and the financial squeeze and to supply intelligence about the terrorist network.

The hardest part is yet to come, but the war president who is learning on the job is making progress on all fronts. He has shown unexpected flexibility. He had started out with a go-it-alone foreign policy, turning his back on international agreements, scoffing at the United Nations, and criticizing “nation building.” Now, with the Taliban in retreat, he sees the need for allies and asks for U.N. help in organizing an interim government in Afghanistan.

We can hope that he shows the same flexibility as he faces the question of paying for the war on terrorism. Officials estimate that it is costing $1 billion a month, and they expect that figure to rise as the United States begins large-scale ground operations. The big tax cut that was to have been the centerpiece of his first year might have to be reconsidered. Likewise the missile defense project, which seems ill-fitted to a new array of international threats, even if it did prove to work.

The war president faces many such difficult decisions as he leads the country through unforeseen dangers. As a man who began determined to preside over a domestic agenda, he deserves credit for showing his reach and skill internationally in ways never expected.