Earlier this year, on her first European tour as U.S. secretary of state, Condoleezza Rice set tongues wagging by strutting into Germany wearing a powerful, all–black ensemble: tall boots, long, military–style jacket, above–the–knee skirt. The backlash to such coverage was not far behind. “I don’t recall any commentary about Colin Powell’s fashion sensibilities,” said one observer. “Do we really want our politicians to face the same scrutiny as our musicians, actors, and Paris Hilton?” asked another. The truth is, in geopolitics, fashion does matter—for men as well as women. Leaders are inevitable symbols of their respective nations, and their fashion choices, with all their subtlety, increasingly shape and reinforce global perceptions, for good and ill.

As if to combine the great military strategist Sir Basil Liddell Hart’s writings on tank maneuvers and high fashion of a century ago—yes, he was an authority on both—Rice’s charm offensive reminded Europe’s onlookers that the United States is a force to be reckoned with. Robin Givhan of the Washington Post said that Rice “looked as though she was prepared to talk tough, knock heads and do a freeze–frame ‘Matrix’ jump kick if necessary.” If the newly appointed top diplomat wanted to show the world that she—and the United States, by extension—is up to the simultaneous challenges of a second term, a war on terror, and an ongoing morass in Iraq, she couldn’t have dressed more appropriately.

Rice may have learned a thing or two about sartorial symbolism from her boss. U.S. President George W. Bush knows that it is often not a leader’s own apparel that matters, but the clothes he asks others to wear on his turf that can...