Al-Qaeda has provided the answer many times. Osama bin Laden, the one whose presence in Afghanistan presumably makes it the central front in the war on terror, has been explicit that ``the most serious issue today for the whole world is this Third World War that is raging in Iraq." Al-Qaeda's No. 2, Ayman al-Zawahiri, has declared that Iraq ``is now the place for the greatest battle of Islam in this era.''

And it's not just what al-Qaeda says, it's what al-Qaeda does. Where are they funneling the worldwide recruits for jihad? Where do all the deranged suicidists who want to die for Allah gravitate? It's no longer Afghanistan, but Iraq. That's because they recognize the greater prize.

The Democratic insistence on the primacy of Afghanistan makes no strategic sense. Instead, it reflects a sensibility. They would rather support the Afghan War because its origins are cleaner, the casus belli clearer, the moral texture of the enterprise more comfortable. Afghanistan is a war of righteous revenge and restitution, law enforcement on the grandest of scales. As senator and presidential candidate Joe Biden put it, ``If there was a totally just war since World War II, it is the war in Afghanistan.''

If our resources are so stretched that we have to choose one front, the Martian would choose Iraq. But that is because, unlike a majority of Democratic senators, he did not vote four years earlier to authorize the war in Iraq, a vote for which many have a guilty conscience to be now soothed retroactively by pulling out and fighting the "totally just war."

But you do not decide where to fight on the basis of history; you decide on the basis of strategic realities of the ground. You can argue about our role in creating this new front and question whether it was worth taking that risk in order to topple Saddam Hussein. But you cannot reasonably argue that in 2007 Iraq is not the most critical strategic front in the war on terror. There's no escaping its centrality. Nostalgia for the ``good war'' in Afghanistan is perhaps useful in encouraging anti-war Democrats to increase funding that is really needed there. But it is not an argument for abandoning Iraq.