Tonight, President Bush will justify his escalation of the Iraq war by arguing the need to succeed.

A new base for state-sponsored terrorism, greater power for Iran, misery for millions of Iraqis, regional instability and even regional war could result from our continuing failure in Iraq.

Unravel the twisted logic, though. The need to succeed is unrelated to the probability of success. That we need to “win” does not make us more likely to do so. While necessity may be the mother of invention, it is hardly the guarantor of success. I may get myself into a situation where I need to win the lottery to avoid bankruptcy. Sadly though, that need will not increase my chances of selecting the winning ticket.

Need does increase commitment. We are already slated to spend nearly $400 billion on the war in Iraq, and the Congressional Budget Office estimates the total cost will be nearly $800 billion – more than the amount we spent (in constant dollars) on World War I, Korea and Vietnam. If Nobel Prize-winning economist Joseph Stiglitz is correct, the total cost could top $2 trillion -serious financial commitment by any reckoning.

But the need for success does nothing to enhance the odds of victory, nor does it argue for the president’s plan as the most likely road to success. While the chances of “victory” are not quite as low as my probability of winning the lottery, President Bush’s escalation is unlikely to achieve its goals.

It certainly hasn’t worked before. Twice since June the U.S. has surged forces into Baghdad – and we are talking about it again precisely because it failed twice before.

It didn’t work then, and it won’t work this time, in part because Bush’s plan ignores the lessons of military science. Students of counter-insurgencies around the globe have developed a simple rule of thumb. Success requires 20 security people for every 1,000 individuals in the population. Thus, securing Iraq requires some half a million personnel. The Pentagon claims that there are about 300,000 trained Iraqi soldiers and police. Add 150,000 American troops and we begin to get close to the magic half million. However, the administration admits that a third of these Iraqi forces are actually “on leave” at any one time. Our 150,000 and their 200,000 leave us woefully short of the security personnel necessary to effectively fight the insurgents.

Moreover, the Iraqi forces, often tools of the militias we are trying to rein in, are not always very effective. The Los Angeles Times reported Sunday that security had collapsed in Diyala province despite U.S. forces having killed the leader of al Qaeda in Iraq there six months ago. Why? Because the U.S. handed security over to Iraqi forces “which have been implicated in so many abuses that the U.S. commander here