What I remember most about serving with the U.S. Marine Corps in Iraq was realizing the extraordinary level of hatred that the Sunnis and Shia Arabs had for each other.

To understand Iraq today, one must understand the deep religious divisions within the country. The Islamic faith fractured into two very separate sects following a leadership struggle after the death of the Prophet Muhammad in 632 A.D. Muslims who believed that the leader should be one of his descendants became known as Shia while those who believed that the leader should be decided by the community of Muslims became known as Sunnis.

Iraq is approximately 60 percent Shia Arab, 20 percent Sunni Arab, and 20 percent Kurds who are mostly Sunni but identify more strongly with their non-Arab ethnicity. Saddam Hussein was a Sunni Arab and under his rule the Sunni Arabs were the ruling elite of the country. After the collapse of the regime and the introduction of representative government, the tables were turned on the Sunnis, and the Shia, who were poorly treated under Saddam, were easily able to dominate the new constitutionally-elected Iraqi government.

When the U.S. military pulled out in 2011, the Shia-led government of Prime Minister Nouri al-Maliki turned to their worst sectarian instincts and marginalized the Sunni Arabs by essentially pushing them out of the government and alienating them. The conduct of the Maliki government has ignited a Sunni Arab revolt and has created an opening for the Islamic State of Iraq and Syria that would not exist if the Sunni Arabs felt they had any hope of a reasonable future.

At this point, an intervention by the U.S. military, at any level, in support of the Shia-led Iraqi government will only be seen as taking sides in a sectarian conflict. A military resolution to the crisis simply does not exist. Even the Iraqi army now is seen by the Sunni Arabs and by the Kurds as a sectarian Shia Arab military force that to them is little more than just another Shia militia.

The only solution is a political reconciliation. Any U.S. military assistance must be strictly preconditioned on a fundamental change in the Iraqi government. This will send a clear message to the Sunni Arabs and to the Kurds that they will have a voice in the formation of a new government where they will be fairly treated and their respective provinces will receive an equitable distribution of the oil wealth of the country.

The areas of Iraq that have fallen are the Sunni-dominated communities which are deeply opposed to the Shia-led government in Baghdad. These areas have temporarily aligned themselves with ISIS as they previously did with al Qaeda in Iraq when coalition forces were occupying the country.

When the U.S. and our coalition allies were in the country, local Sunni Arab Iraqi insurgents joined forces with jihadis to fight what they perceived as their common enemies. However, this was not a natural alliance and once the Sunni Arabs saw hope for a future in a more inclusive pluralistic Iraqi government, with our assistance, they turned against the radical Islamists forces who were terrorizing their communities and imposing beliefs that were objectionable to local Sunni Arab tribal and religious leaders.

Areas in Iraq not dominated by disaffected Sunni Arabs are not in danger of falling to the ISIS-led opposition forces and a successful conventional military operation will only drive the insurgency underground where they can wage a guerrilla war against the Iraqi government without end.

The time is now to put pressure on the Iraqi government to change.

Rep. Mike Coffman, R-Colo., is an Iraq War veteran.