In a rare appearance in the Pentagon press briefing room, the president announced that the military will be reshaped over time with an emphasis on countering terrorism, maintaining a nuclear deterrent, protecting the U.S. homeland, and "deterring and defeating aggression by any potential adversary."
Those are not new military missions, and Obama announced no new capabilities or defense initiatives. He described a U.S. force that will retain much of its recent focus, with the exception of fighting a large-scale, prolonged conflict like the newly ended Iraq mission or the ongoing war in Afghanistan.
"As we end today's wars and reshape our armed forces, we will ensure that our military is agile, flexible and ready for the full range of contingencies," he wrote in a preamble to the new strategy, which is titled, "Sustaining U.S. Global Leadership: Priorities for 21st Century Defense."
The strategy hints at a reduced U.S. military presence in Europe and says Asia will be a bigger priority. It also emphasizes improving U.S. capabilities in the areas of cyberwarfare and missile defense.
Obama's decision to announce the strategy himself underscores the political dimension of Washington's debate over defense savings. The administration says smaller Pentagon budgets are a must but will not come at the cost of sapping the strength of a military in transition, even as it gets smaller.
In a presidential election year, the strategy gives Obama a rhetorical tool to defend his Pentagon budget-cutting choices. Republican contenders for the White House already have criticized Obama on a wide range of national security issues, including missile defense, Iran and planned reductions in ground forces.
Obama also wants the new strategy to represent a pivot point in his stewardship of defense policy, which has been burdened throughout his presidency by the wars he inherited and their drag on resources.
The new strategy moves the U.S. further from its longstanding goal of being able to successfully fight two major regional wars -- like the 1991 Gulf War to evict Iraqi forces from Kuwait or a prospective ground war in Korea -- at the same time.
The strategy document announced by Obama contained no specifics on the size of expected troop reductions; the Army and Marine Corps already are set to shrink beginning in 2015. The document said the Pentagon will have to find savings in pay and health care benefits for members of the military, but it offered no specifics.
It made clear that while some current missions of the military will be curtailed, none will be scrapped entirely.
"Wholesale divestment of the capability to conduct any mission would be unwise, based on historical and projected uses of U.S. military forces and our inability to predict the future," the document said.
The administration and Congress already are trimming defense spending to reflect the closeout of the Iraq war and the drawdown in Afghanistan. The massive $662 billion defense budget planned for next year is $27 billion less than Obama wanted and $43 billion less than Congress gave the Pentagon this year.
Appearing with Obama to answer reporters' questions about the strategy document were Defense Secretary Leon Panetta and the Joint Chiefs chairman, Army Gen. Martin Dempsey. Panetta in recent months had previewed the main themes of the strategy by emphasizing a need to continue pressuring al-Qaida and paying more attention to Asian security challenges, including China and North Korea.
Factors guiding the Obama administration's approach to reducing the defense budget are not limited to war-fighting strategy. They also include judgments about how to contain the growing cost of military health care, pay and retirement benefits. The administration is expected to form a commission to study the issue of retirement benefits, possibly led by a prominent retired military officer.
The administration is in the final stages of deciding specific cuts in the 2013 budget, which Obama will submit to Congress next month. The strategy to be announced by Panetta and Dempsey is meant to accommodate about $489 billion in defense cuts over the coming 10 years, as called for in a budget deal with Congress last summer. An additional $500 billion in cuts may be required starting in January 2013.
A prominent theme of the Pentagon's new strategy is what Panetta has called a renewed commitment to security in the Asia-Pacific region.
The administration is not anticipating military conflict in Asia, but Panetta believes the U.S. got so bogged down in Iraq and Afghanistan after 9/11 that it missed chances to improve its position in other regions.
China is a particular worry because of its economic dynamism and rapid defense buildup. A more immediate concern is Iran, not only for its threats to disrupt the flow of international oil but also for its nuclear ambitions.