Obama is facing an awful choice.
Committing 45,000 more troops to Afghanistan will not assure victory, McChrystal is telling the president, but denying him the 45,000 troops may ensure an American defeat.
Being forced to make this Hobbesean choice will surely affect Obama's decision on Iran. Seeing what a decade of war has done to his country, he cannot want a third war with a nation more populous than Iraq and Afghanistan combined.
Yet that is where the sanctions regime is inevitably headed.