Telegraph
The electric telegraph (1840s) made information travel faster than any messenger for the first time, collapsing the lag between distant event and decision.
For every previous century of human history, news traveled at the speed of whatever carried it: a galloping horse, a sailing ship, a running man. A dispatch from London to Calcutta took months. Then, on 24 May 1844, Samuel Morse tapped out a line from the Book of Numbers, What hath God wrought, over a wire strung from Washington to Baltimore, and for the first time information moved faster than a human body could. That single fact rewired politics.
Collapsing the lag
An electric current runs down a wire at close to the speed of light, so the telegraph did something no courier ever had: it separated the movement of information from the movement of people and things. A general no longer had to wait for a rider; a merchant no longer priced goods on week-old news; a government could learn of a distant crisis while it was still unfolding. The gap between an event and the decision it forced, the lag that had governed statecraft since antiquity, suddenly shrank toward zero. By the 1850s a dense web of copper was knitting cities and then whole countries into a single nervous system.
Wiring the empire
The hard part was the ocean. A cable laid across the Atlantic in 1858 carried messages for a few weeks and died. Not until 1866, after the giant steamship Great Eastern paid out more than two thousand miles of armored cable from Ireland to Newfoundland, did the link hold, and a message that had taken ten days by the fastest steamer now crossed in minutes. Britain grasped the strategic logic faster than anyone and spent the next decades wiring its empire together: an order from London that once took months to reach India could be answered within hours. The global network was finished in 1902 and nicknamed the All Red Line because it ran from British soil to British soil the whole way. By the 1890s British companies owned roughly two-thirds of the world's submarine cables, and the Cornish village of Porthcurno became one of the busiest communications hubs on earth.
Cables as weapons
Owning the wires meant owning the flow of information, and in war that was decisive. Within hours of declaring war on Germany in August 1914, a British cable ship dragged up and severed Germany's transatlantic cables, cutting Berlin off from direct contact with the wider world and forcing its messages onto wireless, where London could intercept them. That decision paid off in 1917, when British codebreakers read the intercepted Zimmermann Telegram, Germany's secret offer of an alliance to Mexico, and helped push the United States into the war. Control of the cables had become a quiet form of global power.
Every network that followed runs in the groove the telegraph cut. Reuters built a news agency on it; stock markets learned to move in real time on it; the telephone, the undersea fiber that carries almost all intercontinental internet traffic today, and the satellites overhead are all answers to the question Morse first posed in 1844, which is what happens to the world when a message can outrun the messenger.