Sometimes wars go exactly the way the governments or political movements that launch them expect. But more often than not, they don't. The secret to success in launching a war is to be able to wrap it up fast and to know when to stop. Those were techniques that the United States was not able to apply in either Afghanistan or Iraq.

The German army since the 1860s had become the global masters of swift lightning campaigns that demolished opponents in a matter of weeks. Their wars of 1862 against Denmark, 1866 against Austria-Hungary and 1870-71 against France all followed this pattern in their decisive campaigns. But they needed good summer and early fall weather to do it. For in the spring and fall, heavier rains turned roads to mud and prevented rapid advances.

In Iraq, however, U.S. Defense Secretary Donald Rumsfeld and his planners bungled the occupation of Iraq, put far too few ground troops in there to secure law and order, and completely failed to anticipate the Sunni Muslim insurgency that grew to civil war scale over the next three and a half years.

In 1914, Helmut von Moltke the Younger and his planners of the imperial German army were confident that their Schlieffen Plan would crush France in a matter of weeks by the end of August. They planned a colossal enveloping attack swinging through Belgium. But the Schlieffen Plan did not work. The German attack bogged down against the French and was driven back from Paris in the Battle of the Marne. Four years of hellish trench warfare followed on the Western Front.

In 1939, aided by the new tactical doctrines of armored warfare and close air support -- soon to be known as "blitzkrieg," or "lightning war" -- the German plan for a brisk, efficient campaign against Poland that would be conveniently over by fall worked perfectly.

German declarations of war came at the beginning of August 1914 and at the beginning of September 1939. The late Professor Hans G. Schenk, a leading expert on modern European history at Oxford University, liked to remark that the German general staff were so orderly that they liked to start world wars on the first of the month in order to keep their records straight.

At the beginning of the 21st century, advanced industrial societies are far less geared to the rhythms of bringing in their harvests. Also, no great powers have fought directly since U.S. and Chinese forces clashed by the hundreds of thousands in their undeclared war in Korea in 1950-53. But the 1990 Iraqi invasion of Kuwait showed that traditional patterns of history did not end with the collapse of communism. And both Russia and the United States have repeatedly resorted to the direct use of military power to achieve their political and strategic goals over the past two decades.

Despite the arguments of American political analyst Francis Fukuyama to the contrary, the collapse of communism did not mean the "The End of History" and the automatic start of a new, peaceful, open and trusting era among the nations of the world. Even as he argued that view, frightful genocidal massacres killed more than 1 million people in Rwanda and wars of ethnic cleansing rocked the Balkans.

Indeed, Zbigniew Brzezinski, one of the most eminent and effective of modern U.S. national security advisers, once dismissed the Fukuyama hypothesis with a terse comment: "After the end of history comes -- more history."

The coming years of the 21st century look likely to be a grim, ironic fulfillment of Brzezinski's prophecy as governments ruling more and more people compete for increasingly expensive and scarce resources in land, food, oil, gas and precious minerals and metals. It will also be a time to remember that the horrors of history can erupt on unsuspecting societies when they least expect it.