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The Obama administration pivot to the Pacific, formally announced by Secretary of State Hillary Clinton last November and reiterated more recently by the president himself, might appear like a reassertion of America's imperial tendencies just at the time when Washington should be concentrating on the domestic economy. But in fact, the pivot was almost inevitable.

When the Berlin Wall fell in 1989, signaling communism's defeat in Europe, security experts talked about a shift in diplomatic and military energies to the Pacific. But Saddam Hussein's invasion of Kuwait in 1990 led to a decadelong preoccupation with the Middle East, with the U.S. Army leading a land war against Iraq in 1991 and the Navy and Air Force operating no-fly zones for years thereafter. Then came...