Reports on the Bush administration’s efforts to craft a new strategy in Iraq often use the term “surge” but rarely define it. Estimates of the number of troops to be added in Baghdad range from fewer than 10,000 to more than 30,000. Some “surges” would last a few months, others a few years. We need to cut through the confusion. Bringing security to Baghdad — the essential precondition for political compromise, national reconciliation and economic development — is possible only with a surge of at least 30,000 combat troops lasting 18 months or so. Any other option is likely to fail.