In June, NATO's leaders commemorated the 60th anniversary of D-Day, the allied invasion of Nazi-occupied France. This August, they passed up the opportunity to mark the 90th anniversary of the start of World War I, which led to calamities that echoed until the twentieth century's end. But the lessons of the Great War are no less important today, particularly for the United States.

The causes of World War I have long baffled the public and historians. Europe was at the peak of its economic power relative to the rest of the world. Peace among the major European countries had reigned more or less continuously for decades. A technology boom was revolutionizing, indeed globalizing, the world economy. For increasingly rich Europeans, the summer of 1914 seemed a peaceful, lazy time. It turned out to be their last real peace for decades.

That July, terrorists in Bosnia assassinated Archduke Franz Ferdinand of the Habsburg Empire. Austria responded by invading Serbia, Bosnia's neighbor and an "upstart" Slavic power. Russia mobilized to support Serbia, while Germany launched a "pre-emptive" war against France and Russia, invading France via Belgium. Great Britain came to the defense of Belgium and France. By September's end, a general conflagration was underway.

But why did the pieces of the puzzle fall into place as they did? Was it bad luck, miscalculation, or bureaucratic error?

It turns out that the German Army Chief of Staff Helmuth von Moltke was eager for war in the summer of 1914. As historian David Fromkin shows in his recent book Europe's Last Summer , von Moltke feared that Russia was gaining too much industrial strength, and that in a few years Russia could withstand a war with Germany. Moltke wanted to invade and defeat Russia before it was "too late" for Germany to triumph.

The Archduke's assassination provided a perfect pretext. The Germans encouraged their ally Austria to respond by invading Serbia, under the clear expectation that this would trigger war, but in a way that Germany would not be blamed. Fromkin shows that the assassination of Ferdinand merely provided Germany an excuse to fight a European War while it still had, according to its calculations, a chance of winning.

Every calculation proved to be disastrously wrong. Imperial Germany was not threatened by Russian industrial dominance in the way von Moltke feared, and its military calculations also failed. Germany did not knock out France and then conquer Russia. Instead, the war ground to a bloody stalemate. Eventually, Czarist Russia collapsed, opening the way to the Bolshevik Revolution.

Germany's launch of WWI ninety years ago this month had a more devastating effect on the world economy than any single event in human history. The war bled Europe of a generation of youth, and set the stage for a second war a generation later. It opened the way for 75 years of Soviet communism, and set in motion the financial instability that led to the Great Depression as well as the collapse of the international trading system.

All of this matters now because last year America launched a war in which a terrorist attack was also an excuse, not the real cause. The Bush administration wanted to fight Saddam Hussein well before the terrorist attacks on the US of September 11, 2001, but it could not have gained public support.

Just as Fromkin shows with regard to Germany in 1914, the Bush administration manipulated US public opinion to support the Iraq War as a war on terror, even though Iraq had nothing to do with any terrorist attack against the US. The world was never fooled by the Bush administration's case, but most Americans were fooled, at least for a while.

We know from a long trail of documents, memoirs, and interviews that the terrorist attacks of September 11, 2001 were a pretext. Richard Cheney, Donald Rumsfeld, and Paul Wolfowitz wanted war with Saddam all through the 1990's, and urged "regime change" as a policy for President Clinton, who wisely rejected such irresponsible advice.

Their eagerness for war had several causes. They wanted to seize control of Iraq's oil. They wanted a new "home base" in the Middle East if Saudi Arabia soured. They wanted to protect Israel from Saddam. They also had exaggerated fears about American weaknesses, just as von Moltke had exaggerated fears about German weaknesses vis-à-vis Russia.

As we know from WWI, wars founded on lies are likely to produce a series of disastrous unforeseen consequences. The ricochet effects of the Iraq War have combined to yield a mounting threat to stability and security. Perhaps the aggressive actions of the US and a resulting backlash in the Islamic world will contribute to nuclear proliferation in Iran, or to nuclear Pakistan someday falling into the hands of extremists.

World leaders should still gather to commemorate WWI, in the hope that they might learn enough to avoid repeating its disaster in our time. The Iraq War is not WWI. We still have time to avoid further devastating mistakes, but only if we are honest about motives, means, and ends - and only if we are honest in the pursuit of peace.

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