As President Bush prepares to unveil his new plan for Iraq this week, just as important as the technical details of strategy, he needs to explain why we’re there, who we’re fighting, and what he would consider victory. It won’t be enough to make the case from a negative perspective (i.e. the consequences of withdrawal), but a positive argument for what we hope to achieve there. When the conflict was mainly against the Sunni insurgency and foreign terrorist groups, it was easier to explain to the American people that we needed to defeat those groups to foster a stable government and deny an Iraqi base to terrorist organizations. Now that the conflict is about sectarian violence (or a civil war if you prefer), it’s a lot more difficult to define victory or even identify the enemy. What especially complicates things is that Maqtada al-Sadr seems to have all the influence with Prime Minister Maliki, who has proved either unwilling or unable to crack down on Shiite militias. Public support for the war has eroded not because the American people are naturally a bunch of surrender monkeys, but because Americans have an increasingly hard time understanding what we intend to accomplish in Iraq at this point. If President Bush has any hope of gaining support from Americans for increasing the number of troops or any other aspects of his plan, he’s going to have to clearly define the enemy and explain what victory would look like.