I recommend Victor Davis Hansons's recent article A War of Endurance. He outlines the stark choices we face in Iraq, and they are the same choices we will face in the inevitable future actions against other failed states that harbor terrorists.
It's clear the rules have changed, and that we are still struggling to figure out the new rules for the sort of prolonged, low intensity warfare we are seeing in Iraq and Afghanistan. It's also clear that America will never prevail in such conflicts if the American people cannot be brought to understand and support long-term military commitments, with the accompanying casualties, in support of our own long-term safety. Our enemies have deduced from our experiences in Vietnam, Somalia, Lebanon, and other places that if they can prolong the battle and the steady trickle of casualties long enough, American public opinion will eventually force us to withdraw.
It seems to me that the military is already doing their part pretty well in learning from their Iraq experiences and innovating tactics to meet the new challenges. But I don't see the political structure of either party doing their part yet - (a) learning how to decide wisely when it is and when it is not worth committing American troops and (b) learning how to gain and maintain long-term public support for these sorts of prolonged military actions.