I would give the Suez Canal the nod. Digging it did much the same for British sea power as Panama later did for the United States. It granted the Royal Navy ready access to the Indian Ocean, making possible a liberal empire presided over by an unrivaled fleet. How crucial Suez was to Atlantic powers’ endeavors in Asia became clear in 1904 and 1905. That’s when Japan’s ally, Great Britain, closed the canal to the Russian Navy — and in turn compelled the Russian Baltic Fleet to undertake an epic 20,000-mile voyage around the Cape of Good Hope, through the Indian Ocean and South China Sea, and up through the East China and Yellow seas just to meet Japanese Adm. Togo’s tanned, rested, and ready Combined Fleet at Tsushima Strait. The result was predictable: a debacle of the first order.