Europe tears itself apart in the first half of the 20th century. Warfare becomes global and civilians suffer severely. Ocean forms both avenue for the flow of resources, goods, and people, but also for an arena. New weaponry below the surface and above it complicate war at sea.

As a triumph of the industrial revolution and its focus in the Atlantic, for the first time in history one region seemingly dominates the entire globe. Its ocean becomes a great vehicle for the flow of resources, people, and ideas. Immigration transforms cultures.

Emotion pushes war. America goes to Cuba to fight a Spanish colonial government. The war spreads to Asia and the United States becomes a colonial power stretching into the far Pacific, filled with uncertain strategic implications.

Exploiting the new age of steel, Americans use this new industry to build a modern navy although on a modest basis. Americans begin to perceive its application to international affairs.

Occupying their own West preoccupies Americans, and they do not react quickly to changing uses of the sea, which the industrial world is creating. The American merchant marine disappears.

American space and resources enabled the rise of a new presence on the international seas. Establishing a powerful place in the world of sail, the nation falls into civil war.

Japan makes what the Atlantic world considers a remarkable leap into regional power and modernity. Defeating Russia generates both admiration and fear about Japan as it builds a colonial presence.

Germany emerges as a great power in the later 19th century and ultimately challenges Britain at sea.

In a protracted struggle, a small but rich Britain pushes aside France on the sea and emerges as the world’s unquestioned salt water power.

Britain retreats from North America but builds a new empire with its strategic center in the Indian Ocean. India becomes the “Jewel of the Empire.”