Iraqi forces are engaged in combat with Islamic State fighters in and around the town of Tikrit. The battle intersects with Benjamin Netanyahu's speech to the U.S. Congress on Tuesday. Netanyahu concentrated on the threat posed by Iran's nuclear program. However, Iran is also engaged in the battle against the Islamic State. The complexity of the U.S. relationship with Iran is summarized in those two thoughts.
Tikrit was the birthplace of Saddam Hussein and a center of Sunni power in Iraq. It fell early to Islamic State forces or, to put it differently, segments of the Sunni community alienated by the Shiite-dominated Iraqi government who joined forces with the Islamic State. Therefore, the battle for Tikrit has political as well as strategic implications. If the Iraqi army takes Tikrit, it will be a significant defeat for the Islamic State. Given that the Iraqi army is predominantly Shiite, it will represent another step in compressing the space the Islamic State occupies and further diminishes its reputation for effectiveness.
This is clearly something the United States wants to happen. The complication is that Iran is sending advisers to the Iraqi forces — both the official army and various Shiite militia groups involved in the battle. For Iran, there are two issues driving this involvement. First, Iraq is a traditional adversary to Iran, and under Hussein's leadership fought a bitter war in the 1980s that cost the Iranians nearly a million casualties. An Islamic State-dominated Iraq would be an unacceptable strategic threat to Iran. Second, Iran is supporting the government of Bashar al Assad in Syria, with Iran's client, Hezbollah, also deeply involved in the battle against the Islamic State. While less of a threat than Iraq, Syria is not trivial to Iran.
Iran and the United States share enemies. The United States, taken by surprise by the Islamic State's rise, has been struggling to contain it without committing significant ground forces. The United States has conducted airstrikes against the Islamic State both in Iraq and in Syria and has committed a small number of troops to the fight. The United States does not want to see the Islamic State in control of significant portions of Iraq or Syria, nor does it want to re-engage in Iraq with multi-divisional forces.
Therefore, the United States wants the Iraqi forces to win in Tikrit. And therefore, to the extent that the Iranians are helping to make this victory possible, the United States and Iran are pursuing the same goal, at least for the time being. It is not clear how much coordination is going on between them, and there has been speculation of some. But even if there has been no coordination the two countries are pursuing the same ends.
In his speech to the U.S. Congress, Netanyahu, focusing on nuclear weapons, argued for increased pressure on Iran. At the same time, the United States is committed to defeating the Islamic State, at the very least sharing a goal with Iran. If the United States were to assert substantial pressure on Iran, there might be two unwelcome consequences. The pressure might force Iran to reduce its support for Iraqi forces, strengthening the Islamic State. Even if that were not the case, and Iran continued to support the anti-Islamic State forces and succeeded in defeating them, the political outcome in Iraq might be as unpleasant for the United States as an Islamic State victory.
Netanyahu's previous arguments for the United States' placing strong pressure on Iran did not have to take into account the current situation. The Islamic State represents a regional threat to U.S. interests. The United States does not want to send large numbers of troops to Iraq and therefore has to be pleased with Iranian support to Iraqi troops. The United States also has to shape the relationship with Iran to make certain that victory over the Islamic State does not lead to Iranian hegemony. That means the United States must continue to be engaged with the Iraqi military even more than the Iranians, providing advisers and substantial supplies.
The Iranians are not all-powerful in Iraq, but they have substantial influence. Iran needs U.S. supplies and airstrikes in the fight against the Islamic State as much as the United States needs Iranian support. Imposing the kinds of pressure Netanyahu wants on this delicate ballet in Iraq is not impossible; it is just enormously difficult. Ultimately, the United States must decide what its primary strategic requirement is at this point. If it is to defeat the Islamic State, then turning on Iran would not be easy. If it is to deal with Iran, then the outcome in Iraq might prove unsatisfactory.
There are circumstances in geopolitics where there are two possible roads, both leading to desirable outcomes. It is sometimes possible to travel down both roads, or to hope that nothing bad happens if you only choose one. But given Murphy's Law, even if you focus on one, things can go wrong. If you focus on two contradictory things and hope to get both, something is sure to go wrong. This is not an argument against Netanyahu's advice. It simply points to a serious difficulty in following it.