Both World Wars of the 20th century, in my view, started too late, with catastrophic consequences for Western Europe. America's Civil War, by contrast, was a war that began just in time, and I attribute the future flowering of the United States to Abraham Lincoln's ruthlessness in pushing the country into war.

General Ulysses S Grant, the Northern commander-in-chief and later president, wrote in his memoirs that the Civil War began with America's 1846 invasion of Mexico, which seized territory to permit the expansion of slavery. Because cotton destroyed land within a decade, the slave-owning caste required perpetual expansion of the slave system into new territories. The Southern Confederacy planned to march southward and create a slave empire in Mexico and the Caribbean (Happy birthday, Abe - pass the blood, February 10).

Was it coincidence that France, England and Spain determined to invade Mexico after Benito Juarez suspended debt-service payment to Mexico's European creditors in 1861, just as the American Civil War began? French, English and Spanish forces landed in Mexico in December 1861, after the South's early victories in the Civil War convinced European governments that the slaveholders would prevail. By 1862, after Stonewall Jackson's success in the Shenandoah Valley, England came close to recognizing the Confederacy. In October of that year, William Gladstone, then chancellor of the exchequer, stated, "We may anticipate with certainty the success of the Southern States so far as regards their separation from the North." The Union half-victory at the Battle of Antietam in September came just in time to abort British recognition of the South.

Had the war broken out two years later, the European powers already would have been entrenched in Mexico, providing the South with a natural ally against the Lincoln government, and a base with which to expand the slave system southward. America would have split in two (at least), and the history of the world would have been radically different, and radically worse.