President Obama's re-election night speech was big and eloquent, as though America had just won a war. He spoke of "perfecting" the union, of "triumphing over war and depression."

"We have fought our way back," he said, "and we know in our hearts that, for the United States of America, the best is yet to come."

We'll see.

Never let it be said that Barack Obama is a humble man. Any president who just won re-election has a right to be proud, but comparing the moment of an electoral victory to the nation's triumphs in war is a bit much.

The president will face many tough challenges over the next four years. In a few weeks, he must decide how to handle the "fiscal cliff" and the budget-sequester crisis. In 2014, the pain from Obamacare, so far deferred, kicks in. This is likely to be one of the shortest honeymoons in history.

But I wager his most humbling moments won't come from these battles. The hardest hits often come from the blind side, and my bet is that his most difficult moments will be where he least expects them — in foreign policy.

Already the resignation of CIA Director David H. Petraeus has surprised everyone. That story continues to unfold and has cast an entirely new spotlight on the controversies surrounding Benghazi, Libya. Congressional hearings are scheduled, and the State Department must report in December on its investigation. Most of Mr. Obama's national security team seem to be heading for the exits. It didn't take long for this particular foreign-policy scandal to take a bite out of Mr. Obama's honeymoon.

Other, more dangerous challenges will come from other places. The most difficult will be from Iran, which contemptuously rejects every naive effort at engagement. Mr. Obama will likely search for a "grand bargain" with Tehran, one that persuades Israel not to attack Iran's advancing nuclear program. Iran is unlikely to cooperate. As time runs out, Israel will feel forced to take matters into its own hands. When it does, Mr. Obama will be upset more so with Israel than Iran, and it will show. If the Middle East explodes in war, the president will, as with other Middle East crises, likely act bewildered and disengaged. The ensuing bloodshed will test him like never before, possibly making his "lead from behind" demeanor in Libya look positively Churchillian.

Then there will be Syria. If President Bashar Assad ever goes, he will more likely be replaced by an Islamist regime than a pro-Western democratic one. Were that to happen during a war between Israel and Iran, Israel could face fighting on two fronts. How would Mr. Obama respond to that? Call the United Nations Security Council? Promise Russian President Vladimir Putin support for a Nobel Peace Prize if he helps sort it all out?

Well, you say, at least the war in Afghanistan will be over in 2014. Mr. Obama made it clear in the presidential debate that he wants nothing to do with Afghanistan after that. Does that mean we will leave nothing whatsoever behind? That would surprise not only the Afghans, but our NATO allies, who think we agreed to a residual force of some kind.

If we do leave Afghanistan completely, the chances for a Taliban comeback are very high. How would that look for Mr. Obama's presidency? He may try to persuade Americans weary of war that ending the U.S. role there is a political victory. But if the Taliban return with their al Qaeda cronies, he will not be able to escape blame for a foreign-policy debacle that exacerbates the terrorist threats to America. And he will have squandered hard-won progress that has cost considerable American blood and treasure.

Pundits say Mr. Obama is now in it for the legacy. If so, he'd better change the way he conducts foreign policy. But something tells me he won't.

The reason has to do with a certain attitude we saw on election night.

• Kim R. Holmes, a former assistant secretary of state, is a vice president at the Heritage Foundation.