President Barack Obama's recent trip to the Middle East and Europe included a brief stop in Germany, where he visited Buchenwald, the former Nazi concentration camp.

German Chancellor Angela Merkel was there, and a solid agenda of issues currently exists between the United States and Germany. But, given the focus of the stop, it is unlikely that much business was done. It was, instead, a bookend to Mr. Obama's stop in Saudi Arabia before his speech to the Muslim world in Cairo.

The Germans wouldn't say so, and perhaps didn't think about it, but Mr. Obama's visit to Buchenwald, accompanied by venerated Holocaust survivor Elie Wiesel, had to be painful for them, underlining their national shame over what they did to the Jews during Hitler's time. It might be as if Ms. Merkel visited the Wounded Knee battlefield in South Dakota in company with a Sioux descendant of the Native Americans massacred there in 1890.

Issues currently outstanding between the United States and Germany include differing approaches to the recession. Ms. Merkel has taken a more restrained approach to an economic stimulus package, putting much more weight on the danger of inflation than Mr. Obama has. Since Germany is Europe's largest economy, this sore point is sometimes seen as evidence of a lack of coordination and agreement between Europe and the United States, although, surprisingly, it's not brought public grumbling from the two countries.

Another difference is that Germany has remained reluctant to help the United States by taking prisoners held at Guantanamo. The Germans have been consistently critical of the prison camp and what has gone on there.

Yet another sore point is the unwillingness of Germany as a NATO ally to put its troops into the "hot" part of the Afghanistan war in the south of the country. It currently has 4,500 troops in Afghanistan, but their activities are concentrated in the north, not in the center of the fighting against the Taliban.

This point has an odd, undiscussed corollary. There are still some 70,000 U.S. troops based in Germany. The strategic rationale for their presence is long gone.

After World War II, U.S. troops were based in Germany, first of all, as occupation forces. No one wanted to see a repeat of what happened after World War I ended in 1918, when it took Germany no time to rearm and to be on the move again inside Europe, starting with Austria in early 1938, leading by 1939 to a full-fledged continental war.

The post-World War II occupation then merged seamlessly into the Cold War period, when the United States based thousands of troops in Germany to serve as a bulwark against a possible land invasion by the Soviet Union into Western Europe. Germany itself was divided into Communist East Germany and an evolving, democratic West Germany.

This reason for the presence of U.S. troops in Germany ended when the Berlin Wall came down in 1989, to be followed in 1990 by the reunification of Germany and the full democratization of the country.

But here we are 19 years later, still with thousands of U.S. troops based in Germany, for no obvious reason. The ex-Hitler Youth, such as Pope Benedict XVI, are now in their '80s. Although it might still be possible to argue that the Russians could become obstreperous again, it is clear that whatever they might dream up could easily be deterred, either by waving the nuclear weapons that both sides still have, or by quick deployment of U.S. and other troops back into Germany on a contingency basis. The U.S. relationship with Russia, although sometimes a little tetchy, is basically a matter of diplomacy these days.

So what is it that prevents the Germans from asking ever so politely that if the United States wants more troops in Afghanistan, why doesn't it just deploy some of the 70,000 it has based in Germany? Or, put another way, from the German and American points of view, what is the rationale for keeping U.S. troops in Germany these days?

On the German side it is financially profitable. Germany is an expensive place to live and work and the U.S. presence there puts millions into its economy. This is pure expense on the U.S. side, so there is no good reason for the troops' continued presence from the point of view of the U.S. taxpayer.

Again from the German point of view, the U.S. troops allow Germany to not spend as much on its own defense. Although the Europe of 2009 is a very different place from that of the 19th and 20th centuries, there have been times when Germany lived in a dangerous neighborhood, given its frequent differences with France, Russia and others. Germans who still have national nightmares about what its leaders did in both world wars are no doubt quite happy not to see Germany feel a need to rearm as much as it might otherwise, due to the presence of the U.S. forces.

So, really, the only loser in the current arrangement is the U.S. taxpayer, who maintains thousands of troops and many bases in expensive Germany, as opposed to bringing them home and deploying from the American homeland. And it is a little crazy to have U.S. forces based in Germany unnecessarily while we harass the Germans to send their troops to Afghanistan.

If the argument is that it is easier to deploy U.S. troops to the Middle East or elsewhere from Germany than it would be from the United States, then the question is, why does the United States have to have a deployable overseas presence in any case? Isn't that what all its ships and airplanes are for?