On February 15, 1898, the USS Maine exploded in the Havana Harbor. Although there was no evidence that the Spanish were responsible, yellow newspapers such as William Randolph Hearst's New York Journal whipped Americans into frenzy by claiming that Spain's "secret infernal machine" had destroyed the battleship. Soon after, the blandly handsome and easily influenced President McKinley declared war, sending troops not only to Cuba but also to the Philippines, Spain's sprawling colony on the other side of the world.As Evan Thomas reveals in his rip-roaring history of those times, the hunger for war had begun years earlier. Depressed by the "closing" of the Western frontier and embracing theories of social Darwinism, a group of warmongers that included a young Teddy Roosevelt and Henry Cabot Lodge agitated loudly and incessantly that the United States exert its influence across the seas. These hawks would transform American foreign policy and, when Teddy ascended to the...