PRESIDENT OBAMA pledged that the $489 billion in defense cuts he has proposed over 10 years would be governed by a concerted strategy, and on Thursday he delivered one. At the Pentagon, Mr. Obama unveiled a “strategic guidance,” which aides said reflected a considerable investment of his personal time and ideas. The president’s thesis is that the need for fiscal austerity coincides with a global “moment of transition,” in which the United States is winding down a decade of land wars in Iraq and Afghanistan and facing the need to turn toward a very different set of challenges, particularly in Asia.

Several previous administrations have tried to shift to Asia from the messy Middle East, only to be dragged back by wars, terrorists, turmoil and the unending need to protect allies and the flow of oil. The Obama strategy acknowledges that history and says this pivot will be different. The means to reduce spending and build capacity in Asia, it suggests, will come not from the Mideast but from U.S. deployments in Europe, benefit and retirement costs, Cold War weapons systems and the U.S. nuclear arsenal.

Though the administration has yet to spell out specifics, in principle these are sensible areas to look at for savings. We have argued previously that the military’s health-care system, which consumes $50 billion a year and charges military personnel premiums that are one-tenth of those of other federal employees, is unsustainable. Though the administration already has cut or canceled 30 weapons systems, saving some $300 billion, more could be trimmed. Whether benefit cuts could be pushed through Congress during an election year is open to question, but under the circumstances the president would be right to try.

A more dubious, and risky, assumption of Mr. Obama’s plan is that the United States will no longer conduct operations like those of the last decade: “long-term nation-building with large military footprints.” Though counterinsurgency has produced results in both Iraq and Afghanistan, it — and the troop levels required for it — will be retired; the size of the Army and Marines will be returned to prewar levels. This, too, is not a new concept: After Vietnam, the Pentagon abandoned counterinsurgency and planning for troop-intensive operations.

Mr. Obama acknowledges that was a mistake, and he vowed Thursday not to repeat it. His solution is what the Pentagon is calling “reversibility.” Officials say the expertise and some of the officer cadre necessary to carry out counterinsurgency and nation-building will be preserved, so that the capacity could be restored if needed.

Even if that works, the judgment that such operations can be ruled out for the next decade strikes us as at odds with the reality of a Middle East in revolution, an increasingly belligerent Iran and a North Korea undergoing an unpredictable leadership transition — to name just the most obvious threats. Afghanistan itself is due to be the site of U.S. counterinsurgency operations until 2014, and tens of thousands of troops will remain for many years afterward if a pending deal with the Afghan government is completed.

No one wants war with Iran or North Korea, but if one occurs, a major U.S. land force will be needed for a prolonged period. And if central authority dissolves in Yemen and a threat to the U.S. homeland emerges from al-Qaeda forces there, what will be the response? Mr. Obama’s strategy seems to assume that counterterrorism operations — such as the drones that circle al-Qaeda targets in Pakistan’s tribal territories or raids by special forces — will be sufficient. The history of Afghanistan before 2001, and the deteriorating situation in Pakistan today, suggest otherwise.

To be sure, if hard budget choices must be made, it is probably wiser to reduce troop levels than to curtail investments in new planes and ships or in new weapons technology. But this raises the question of whether the scale of the defense cuts the president is considering is appropriate. According to Deputy Defense Secretary Ashton Carter, under Mr. Obama’s plan “you have over the next four years a reduction in total defense spending as rapid as any we experienced after Vietnam or after the Cold War.” Both those drawdowns are now almost universally regarded as having been unsustainable and shortsighted.

Moreover, another $500 billion in across-the-board “sequestration” cuts will take effect in 2013 unless Congress repeals them. Defense Secretary Leon Panetta and the Joint Chiefs have said that such a fiscal hit would be a catastrophe for U.S. defense. But Mr. Obama did not speak against it Thursday. In fact, he has vowed to veto any bill that is limited to repealing the Pentagon sequestration. He seems to be trying to bluff Republicans into accepting other spending reductions or tax increases. But for the commander in chief to toy with measures that would materially damage U.S. national security hardly seems responsible.

As he has before, Mr. Obama cited on Thursday President Dwight D. Eisenhower’s maxim that military spending “must be weighed in light of a broader consideration: the need to maintain balance in and among national programs.” When Mr. Eisenhower spoke those words, defense spending represented more than 9 percent of U.S. gross domestic product. Under Mr. Obama’s plan it would drop from about 4.5 percent to under 3 percent. Meanwhile, other than cuts to finance the new entitlements in his health care bill, the president has yet to propose meaningful trims in the exploding costs of entitlements such as Medicare, which did not exist during Mr. Eisenhower’s presidency. Would Ike have regarded what Mr. Obama is proposing as “balanced”? It’s hard to see how.