In July 1956, Egypt's president Gamal Abdel Nasser did something that the British Empire considered unthinkable. He nationalized the Suez Canal — the single most important shipping route connecting Europe to Asia, and the crown jewel of Britain's post-imperial infrastructure.

Britain didn't take it well. In October, it invaded — alongside France and Israel — expecting a quick, decisive victory that would restore order and remind the world who still ran the show.

Militarily, it worked. The canal zone was secured within days.

But then something happened that no one in London had gamed out. The United States — Britain's closest ally — refused to back the operation. Eisenhower was furious. And he didn't just voice his displeasure diplomatically. He weaponized the one thing that mattered more than tanks or aircraft carriers: money.

Eisenhower threatened to dump America's holdings of sterling bonds. This caused a run on the pound. Sterling had already been under speculative pressure since the invasion began in late October — and the threat from Washington was what tipped that weakness into full-blown panic. The Bank of England (BoE) hemorrhaged reserves trying to defend the pound — over $200 million in November 1956 alone — as the world suddenly lost confidence in the currency. And when the BoE went to the International Monetary Fund (IMF) begging for dollar liquidity, Washington blocked that too.