For nearly two centuries the United States has conducted its Western Hemisphere diplomacy according to the precepts of the Monroe Doctrine, promulgated in 1823 and designed to keep European powers out of hemispheric affairs. America's involvement in Latin America was expanded substantially by the 1904 Roosevelt Corollary to the Monroe Doctrine, which proclaimed American willingness to intervene in the region. And America's reach was extended again by the Truman Doctrine of 1947, designed to contain communism as the Cold War chilled.
Have we just witnessed the expression of the Obama Doctrine, at once more expansive and less ambitious than the doctrines that preceded it?
In two important speeches in recent days, President Barack Obama has shrunk the U.S. role (in Afghanistan, for instance, where troops are to be withdrawn by the end of 2016) even as he expanded the country's global footprint (primarily in Africa and Asia, where the president says new terrorist threats reside).
At the heart of the Obama Doctrine -- a term that he never used and that may be an over-interpretation of its scope -- is the notion that the principal threat to American security comes from a discrete but exceedingly worrisome source.
That threat, according to Obama, comes not from nation-states, which prompted the doctrines of James Monroe, Theodore Roosevelt and Harry Truman. Nor does it come from a centralized terror organization like al-Qaida, the prime preoccupation of American national security efforts for the last dozen years.
That threat also does not come from "trouble spots" -- a classic Cold War locution applied to Berlin, the Korean peninsula and Southeast Asia, especially Vietnam, Laos and Cambodia -- but from troubling rogue groups in places such as Yemen, Syria, Nigeria, Mali, Somalia and elsewhere.
The president could not have made this more plain: "For the foreseeable future," Obama said, "the most direct threat to America at home and abroad remains terrorism."
That sentence, spoken at the United States Military Academy at West Point, New York, contained none of the "Mission Accomplished" bravado of George W. Bush after the second invasion of Iraq, nor any of the soothing reassurance about the eclipse of al-Qaida that Obama has offered in years past. Both expressions today look worse than premature. They look naive -- and dangerous.
The twin Obama speeches were designed to counter Obama's twin rivals, domestic and foreign.
His domestic opponents reacted coolly, asking why the president would provide public notice to the Taliban of the exact moment when U.S. troops would no longer provide a substantial obstacle in Afghanistan and arguing that the president's initiative was just another misbegotten judgment to match those he made regarding Syria and Russia.
The reaction of overseas rivals was more difficult to measure, reflecting the fact that the new emphasis in American national security is aimed at, in the phrase employed by Obama, a "diffuse threat."
Even so, the notion that the United States was embarking on a new era was underlined by an intriguing, even irresistible, coincidence: the primary-election defeat of Rep. Ralph M. Hall, a 91-year-old Texas Republican, on the same day Obama declared that it was "time to turn the page on a decade" of foreign policy focused on wars in central Asia.
Hall's defeat ensures that the new Congress to be seated in January will have no veterans of World War II. Nine American presidents were in one way or another involved in that conflict. All of them, and scores of lawmakers on Capitol Hill, were shaped by the debacle of European appeasement at Munich, by the Allied effort that defeated Nazi Germany and Japan, by the development of American nuclear power and by the growing rivalry with Soviet Russia.
Their view of the world was dominated by the great powers that dominated the world. Although they prosecuted and funded wars at Inchon and around the 38th parallel, and during the Tet Offensive and the Vietnamization effort, they took their lessons from Pearl Harbor and D-Day, and inevitably regarded Washington, London, Paris, Berlin and Rome (plus the United Nations headquarters at Turtle Bay) as the centers of diplomacy and power.
Whether what Obama spoke about this week deserves spelling "doctrine" with an uppercase D or a lowercase one, he set out a more modest American role (expanding American "reach without sending forces that stretch our military too thin, or stirs up local resentments") even as it establishes a wider security horizon (in Asia and Africa).
In the Cold War, American attention tended to be concentrated on one place at a time -- in Europe right after World War II as the Soviet bloc expanded, in Asia as China fell to the Communists and Korea became the setting for a difficult "police action," in Vietnam as Americans divided over whether Southeast Asia might become a communist "domino," and then in Africa as proxy wars were fought in Congo and Angola.
This new threat requires a worldwide focus, which is to say, no particular focus at all.
And, in truth, Obama's vision may be more descriptive than prescriptive, as the United States seems already to have adopted this doctrine.
The power politics of the 19th and 20th century has seemed passe throughout the Obama years, which is one reason the response to the Russian advances in Ukraine seemed so tepid. Large nation-states still dominate the globe and threats still reside in countries such as Iran and North Korea. But most of the gunfire and explosives come from decentralized terrorist cells scattered about the globe.
It is those groups that have the attention of Obama and that prompted his proposal for a $5 billion Counterterrorism Partnership. And it is those groups whose activities the Obama Doctrine -- flawed or limited or perhaps too modest -- is designed to counter.
The doctrines that preceded Obama's were conceived as long-term if not permanent themes in American foreign policy. The longevity of Obama's doctrine will be determined by whether it succeeds or fails in the short term.
David M. Shribman is executive editor of the Post-Gazette. Follow him on Twitter at ShribmanPG.