1: The economy sucks at the moment.
2: The longer a military engagement the more it will cost.
3: Current estimates that a war of less than one month will be good for the economy, and more could push us into a depression.
4: The only way to win a war faster is to take more risks. i.e. Higher casualties.
5: The U.S. military is planning a fast all-out attack. General Myers[NYTimes]: "People are going to die."