President Bush announced yesterday in a campaign speech in Cincinnati his support for a long-aborning Pentagon plan to redeploy U.S. forces overseas.

The basic idea is to move them from what was basically post-World War II and Cold War positioning in Europe and Asia into locations that make them more readily accessible for conflicts in the Middle East.

The moves also reflect the current squeeze on availability of U.S. forces overall, brought about by the demand for some 130,000 in Iraq and 20,000 in Afghanistan. Military doctrine says that to maintain 150,000 troops in a theater requires, in fact, 450,000 troops -- the 150,000 who are there, another 150,000 to rotate in behind them, and another 150,000 who are the ones who were rotated out when the 150,000 who are there now were rotated in, who require retraining and refitting.

The squeeze caused by the Iraq and Afghanistan wars has also required the assignment of more Reserve and National Guard forces for longer and more frequent periods overseas. Those deployments have resulted in considerable inconvenience, partly because unexpected, for those forces and their families, which translates into unpopularity at home for the Bush administration.

These forces' lesser level of preparedness and training by comparison to regular forces has also contributed to problems in Iraq, such as the Abu Ghraib prison scandal.

There has been a need, at least since the end of the Cold War with the Soviet Union and the Warsaw Pact 13 years ago, to adjust American force levels in Europe correspondingly. The old needs to sit on Germany and be prepared to resist a Soviet assault into Western Europe are long gone, but the U.S. troops linger on.

The deployments in Asia, in South Korea and Japan, are more complicated. The United States retains forces in Japan in part to make it unnecessary for Japan to rearm: The thought of a remilitarized Japan gives its Asian neighbors, including China, a major case of nerves.

Another reason the United States keeps forces in Japan and Korea is to have them there in the event the Chinese move on Taiwan, even though nobody wants to say so. U.S. Taiwan policy is to pray that the feisty islanders concentrate on developing their growing economic and political ties with the mainland and not bounce so many rocks off the heads of the Beijing leadership that they lose patience and attack, thus allegedly requiring a U.S. military response.

The U.S. troops in South Korea are justified -- in spite of South Korea's own strong military capability, backed by a powerful economy -- by the military threat of North Korea's million-man army, possibly backed by nuclear weapons. The general assessment now is that North Korea is better dealt with by regional diplomacy, involving China, Russia, Japan and South Korea, than by military force, but the U.S. troops remain.

Mr. Bush's speech yesterday, coupled with the signature by Secretary of State Colin L. Powell earlier this month with Denmark and Greenland of an agreement to upgrade U.S. anti-missile defense systems in Greenland, reveals a Republican strategy to make moves in the field of defense that can be cited as evidence that a second Bush term is America's best guarantee of a vigorous defense posture across the globe.

Two aspects of these moves prompt suspicion. The first is the casting of the announcement: Isn't the redeployment of U.S. troops from Europe and Asia to meet the appetites of the Iraq and Afghanistan wars, in fact, making a virtue of necessity? The reasons to do so are a decade old. The second is the timing of the announcement. The Pentagon has had a redeployment plan on the shelf for years; it is the right thing to do, but why announce it now, two weeks before the Republican convention?