Over the past week, three leaders of important American allies arrived for meetings with President Bush - Prime Minister Recep Tayyip Erdogan of Turkey, President Nicolas Sarkozy of France and Chancellor Angela Merkel of Germany. With each of these countries, the United States has a long alliance history. In more recent times, particularly over the issue of Iraq, however, it has been a history characterized by a certain dissonance and by anti-Americanism.

And yet, it remains true that as with Rome, all roads lead to Washington. In times of a challenge, the world continues to look to the United States for leadership. It remains the case, though, that the United States is the only country able and willing to enforce the international order by military force - to be the world's policeman, if you will. When international concerns go up about Iran's nuclear ambitions, when Turkey threatens to invade northern Iraq, when the Pakistani government looks to be on the verge of collapse, and when Russian authoritarianism is on the rise. Washington still plays the key role in setting the course.

We cannot do it without international partners, though. Alliance maintenance has been one of the major themes of the second Bush administration, which learned some hard lessons from the first four Bush years. An alliance of the willing, as was assembled before the military action in Iraq, is a perfectly legitimate alliance, but the greater the burden sharing among the willing, the greater also the chances of success. Otherwise, a disproportionate and unsustainable burden falls on the United States.

The three visiting leaders each had high-stakes messages to convey. Mr. Erdogan was here to talk about Turkey's problems with Kurdish rebels, the PKK, who use the Kurdish areas of northern Iraq as a base for attacks on Turkey. Turkey is threatening a military invasion to rout them out, which would be a nightmare for the United States.

Furthermore, U.S.-Turkish relations recently avoided sustaining a major blow when the Democratic leadership in the House of Representatives decided to not to push for a vote on the Armenian genocide resolution. Having dodged this bullet, Mr. Erdogan repeatedly went out of his way in his press conference with Mr. Bush to stress Turkey's strategic partnership with the United States.

The French president arrived with the evident determination to rebuild the partnership with the United States that former President Jacques Chirac had done his best to destroy in the run up to the Iraq war. In his address to Congress, Mr. Sarkozy told American legislators, "In times of difficulty, in times of hardship, friends stand together. I want to be your friend, your ally, and your partner." Mr. Sarkozy's rhetoric has been so splendid that it has barely been noticed that the additional commitments he made in Afghanistan on behalf of France remain safely in the soft-power areas of police training and reconstruction. But Americans always feel best in the glow of international approval, and Washington has responded with great enthusiasm to this novel and friendly French approach.

Clearly, it is very much in the interest of France to restore relations. Because of the hubris shown by Mr. Chirac and his hopeless foreign minister, Dominique de Villepin, who tried to make France (with the EU behind it) a power center competing with the United States, French international influence actually declined. Mr. Sarkozy speaks forthrightly about restoring French influence in the world, and he has made the reasonable calculation that this is best done by partnering with the world's most powerful country rather than fighting it.

The German chancellor meanwhile came to the Bush ranch in Crawford, Texas to talk about Iran, a subject of great domestic concern for her. This is in part because of Germany's extensive financial links with Iran, and also because German pacifism is such that a U.S. attack to deal with Iran's nuclear program is a horrifying idea for her Social Democratic coalition partners. Germany even remains opposed to sanctions on Iran outside a U.N. framework.

But at least Mrs. Merkel is trying to work through her differences with the White House through consultations and dialogue, not derisive public position as characterized her predecessor Gerhard Schroeder's approach to American leadership. The fact is that with its export credits and investments in Iran, we need Germany on board before sanctions can be effective. Doing business even with U.S. allies can be frustrating and difficult, but such are the challenges of leadership.

Helle Dale is director of the Douglas and Sarah Allison Center for Foreign Policy Studies at the Heritage Foundation.