We Americans, despite our current grumblings, are fundamentally an optimistic people. Our optimism has helped us achieve great things. But it can also be a problem. There is an assumption in public life that every problem has an optimum solution, all gain and no pain. Much of our political debate takes the form of yelling that everything would be just fine if the other side weren't so stupid that it failed to see the perfectly obvious policy.

The debate over Iraq has often been based on this assumption. The Bush administration has been blasted for dissolving the Iraqi army (actually, allowing it to disperse), which left it harder to maintain order. But maintaining Baathist officers in place would have produced much oppression and left weapons in the hands of many determined enemies. There was no optimum solution here -- there were serious downsides to either policy.

A superficial view of our history buttresses the assumption that there's always an optimum policy. In times of crisis, we seem always to have found great leaders -- Washington, Lincoln, Franklin Roosevelt. In war, we have always surged through to victory.

Our economy has grown so bounteously that we have come to take its miraculous performance for granted. But this line of thought leaves out some inconvenient facts. We've had some pretty awful leaders -- the politicians of the 1850s who led us toward civil war, Woodrow Wilson after his incapacitation, who prevented ratification of the Versailles Treaty.

We haven't won all our wars: the War of 1812 and Korea were ties and Vietnam ultimately a loss. Our economy has gone through some pretty rough patches, caused by what are now recognized as major policy mistakes -- the depression of the 1930s and the stagflation of the 1970s.

And sometimes we have been faced with tragic choices. Just 65 years ago, just after Pearl Harbor, Winston Churchill spent Christmastime at the White House conferring with Franklin Roosevelt. Optimum solutions were not in sight. The American fleet was still smoldering, the Japanese were streaming into the Philippines and headed into Malaya (with its rubber) and Singapore. Nazi troops were on the outskirts of Moscow (you can see the monument marking their farthest advance on the highway in from the airport today), and U.S. military leaders all believed that the Soviets would be defeated within months.

But Churchill and Roosevelt were determined to move forward, even (as in the North Africa invasion of November 1942) against the advice of their military leaders. And they both without hesitation chose to support the Soviets, even though they were well aware of the evil of Stalin's regime -- and understood that in destroying Hitler they were risking Soviet enslavement of Eastern Europe.

We forget now, but there was opposition to Roosevelt's decision to go after Hitler first (hadn't we been attacked by the Japanese, not the Germans?) and to support Stalin (an indubitably evil leader). And there were many times -- not just moments, but agonizingly long months -- when it seemed that victory was impossible. Our military strategy and tactics were far from perfect. And the Soviets did gobble up Eastern Europe and North Korea, as well. But the less-than-optimum choices Roosevelt and Churchill made, in retrospect and on balance, look preferable to any alternatives.

George W. Bush now faces an array of less-than-optimum choices on Iraq. On the campaign trail and on Sunday interview shows, many Democrats and a few Republicans for months blithely talked of withdrawal. But as they have faced the probable consequences, spelled out by among others the Baker-Hamilton Iraq Study Group, the downside risks seem ominous.

Nor does the ISG's recommendation that we negotiate with Iran and Syria look at all promising, given the recent behavior of Iran's Ahmadinejad. Debate continues on military tactics. Should we embed more trainers in Iraqi units? Should we surge some 35,000 or so troops in to pacify Baghdad? The success of military tactics, as Churchill and Roosevelt knew, is never certain. But the challenges before us are surely not as daunting as assaulting Hitler's Fortress Europa and reclaiming the Pacific from Japan.

Bush has stressed that he has followed the advice of his military leaders. But he needs to do more. He needs to engage now with his new secretary of defense and his military leaders, in the aggressive and detailed way that Churchill and Roosevelt did, probing and critiquing their proposals, eliciting from them plans that can reduce the sectarian violence in Baghdad and the Baathist and Al-Qaida attacks there and in Anbar province to tolerable levels. Even over Christmas, as Churchill and Roosevelt did.