In a distant wing of the sprawling building, he located the test caisson where armor experts simulated torpedo attacks to measure the awesomely magnified impact of explosions underwater. He rummaged through their magazine. The sea powers locked in the international race to build modern dreadnought battleships were feverishly experimenting with arming torpedoes with TNT, but Yamamoto noted that the Americans were still testing formulations based on guncotton propellants. He stole a silk bag of Cordite MD smokeless powder.

As he opened a janitor’s closet to filch a bottle of ammonia water, he heard a watchman coming. He hid in the closet until the old fellow had shuffled past and disappeared among the guns.

Swift and silent, Yamamoto climbed the stairs.

Arthur Langner’s drawing loft, which was not locked, was the workshop of an eccentric whose genius spanned war and art. Blueprints for stepped-thread breeches and visionary sketches of shells with smashing effects as yet unheard of shared the workspace with a painter’s easel, a library of novels, a bass violin, and a grand piano.

Yamamoto left the Cordite, the iodine, and the ammonia on the piano and spent an hour studying the drafting tables. “Be Japan’s eyes,” he preached at the Black Ocean Society’s spy school on the rare occasions that duty allowed him home. “Take every opportunity to observe, whether your ultimate mission is deception, sabotage, or murder.”

What he saw frightened him. The 12-inch guns on the factory floor could throw shells seven miles to pierce ten inches of the newest face-hardened side armor. But up here in the drawing loft where new ideas were hatched, the Americans had preliminary sketches for 15-inch guns and even a 16-inch, seventy-foot-long monster that would hurl a ton of high explosives beyond the curve of the Earth. No one knew yet how to aim such a weapon when the distances were too great to gauge range by “spotting” the splashes of near misses. But the bold imagination that Yamamoto saw at work warned him it was only a matter of time before America’s “New Navy” invented novel concepts for fire control.

Yamamoto stuffed a wad of paper money in the gun designer’s desk—fifty twenty-dollar U.S. gold certificates—considerably more than what one of the arsenal’s skilled workmen earned in a year.

Already the U.S. Navy was third only to England’s and Germany’s. Its North Atlantic Fleet—brazenly rechristened the “Great White Fleet”—was showing the flag in a swaggering voyage around the world. But Britain, Germany, Russia, and France were not America’s enemies. The true mission of the Great White Fleet was to threaten the Empire of Japan with naked steel. America aimed to command the Pacific Ocean from San Francisco to Tokyo.

Japan would not allow it, Yamamoto thought with a prideful smile.

It was only three years since the Russo-Japanese War spawned in blood a new master of the Western Pacific. Mighty Russia had tried to strong-arm Japan. Today the Empire of Japan occupied Port Arthur. And Russia’s Baltic Fleet lay under three hundred feet of water at the bottom of the Tsushima Strait—thanks in no small part to Japanese spies who had infiltrated the Russian Navy.