He moved fast, hoping to defeat the British army in what is now Belgium before the other allies arrived to reinforce it, and he almost succeeded.
The British commander, the Duke of Wellington, said that the battle of Waterloo was "the nearest-run thing you ever saw in your life". But if Napoleon hadn't lost at Waterloo, he would have been defeated a little later.
"God is on the side of the heaviest battalions," said Voltaire - and Napoleon agreed, just substituting "the best artillery" to demonstrate that his military knowledge was fully up to date. But his political knowledge was woefully deficient: God is actually on the side of the biggest economies, especially if they know how to turn their wealth into military power.
Britain had already overtaken France as Europe's biggest economy (and the world's biggest economy). The industrial revolution in Britain was already into its second generation, while France had barely entered the first. Even in sheer numbers of people, a low birth rate meant that France would fall behind Russia, Germany, and eventually even behind Britain in population.
So even if Napoleon could go on winning battles, he couldn't win the war ... and, in the end, he couldn't even win the battles. He was running out of soldiers, and his enemies had spent a generation at war learning to fight battles just as well as he did. Waterloo only confirmed what everybody with eyes could see already: France was finished as Europe's superpower.
Then Britain got a century at the top. The United States is now about 75 years into its term as the reigning superpower - and you are probably assuming that I am now going to speculate who gets the crown next. Wrong on two counts. First, it's a thorny crown, and nobody in their right mind would want it. The relevant statistic is that the more powerful a country is, the more wars it fights and the more people it loses. More power doesn't give you greater security - it just gets you into more trouble.
Secondly, about half the time there is no undisputed top dog. That was the situation for the century 1600-1700, when Spain was in visible decline but France was not yet ready to assume the mantle of sole superpower.
It was equally true in 1945-1990, when nuclear weapons (the great equaliser) meant that the United States and the Soviet Union were co-equal superpowers even though the US economy was far bigger than the Soviet one.
Now, with the American superpower allegedly in decline, there is obsessive speculation about when China will step in and take over - or might it turn out to be India instead - as though it were still the early 19th century when France was going down and Britain was taking over. It isn't.
Military power doesn't deliver the goods any more. The United States has lost almost every war and mini-war it has fought in the past 50 years (except Grenada and Panama), even though it accounts for around half of the planet's spending on defence.
In the present global strategic environment, decisive victories are about as rare as unicorns. This is not necessarily a bad thing. In fact, it is probably a good thing. Victory is a much over-rated concept.
Gwynne Dyer is an independent journalist whose articles are published in 45 countries.