A coalition of Iraqi security forces, Kurdish Peshmerga fighters, Sunni tribal fighters and Shiite militias launched a much-anticipated offensive to liberate Mosul, the largest city in Iraq, from the Islamic State group, which has occupied the northern Iraqi metropolis since June 2014.

The offensive marks a crucial turning point in the campaign to degrade and destroy the Islamic State group, since Mosul represents the group’s last major stronghold in Iraq. Yet the liberation of Mosul should not be conceived of as an endgame, but an early step in a decades-long process to stabilize Iraq.

Retaking Mosul will certainly not be easy. The Islamic State group has constructed concrete blast walls, dug trenches, and rigged booby traps that will slow efforts to penetrate the city.

Moreover, since more than one million civilians remain in the city, coalition forces will need to slowly clear the city block by block to minimize collateral damage. With the assistance of U.S. combat advisers and air support, however, the coalition should be able to secure the city over the next few months.

Unfortunately, following the liberation of Mosul, the ethno-political fragmentation that spawned the rise of the Islamic State group will remain. The simple fact that the force advancing on Mosul is comprised of government security forces as well as ethno-sectarian militias exemplifies that reality.

In fact, sectarian suspicions remain so intense that prior to launching the Mosul offensive, the Iraqi government felt compelled to secure a commitment from Shiite militias not to enter the majority Sunni city, but to remain on the outskirts.

Given those ongoing divisions, securing Iraq will therefore require more than simply seizing territory from the Islamic State group. Establishing stability demands the construction of an inclusive state that, over the long-term, gradually erodes the sectarian rivalries that continue to divide the country.

The construction of strong, inclusive government security forces is indispensable to that process. And that is an area where the United States can help. Over the past decade, the U.S. military has significantly improved its capability to build the capacity of partner military forces.

Yet the rise and spread of the Islamic State group demonstrated that although the United States can effectively train and equip partner forces, those forces often have difficulty sustaining a high level of competence without ongoing U.S. support. The United States must therefore recognize that constructing strong Iraqi security forces will require a long-term U.S. commitment to train and equip those forces.

Although strong security forces are necessary, they are not sufficient. The construction of a stable Iraqi state requires an enduring political settlement, which provides rival factions with a mutual interest in participating in a democratic governance process. The United States can prod Iraqis toward such settlement and provide various types of governance assistance. Ultimately, though, establishing a durable political settlement is something the Iraqis must accomplish on their own.

Haider al-Abadi, Iraq’s current prime minister, deserves a great deal of credit for striving to foster an inclusive Iraqi government. Whereas his predecessor, Nouri al-Maliki, entrenched his Shiite Dawa party at the expense of Iraq’s other ethnic groups, Abadi has actively sought to enlist greater Sunni and Kurdish participation in Iraqi governance.

In addition, he has attempted to crack down on endemic corruption that has primarily benefited Shiites. Yet those efforts have encountered fierce resistance — from domestic constituents who benefit from the existing system as well as foreign players (most notably Iran) who have an interest in ensuring that Iraq remains fragmented and weak. In the face of such resistance, crafting a durable political settlement will take time.

The beginning of the offensive to retake Mosul is certainly a welcome development. It may mark the beginning of the end for the Islamic State group — at least in Iraq. But recapturing Mosul will merely constitute the end of the beginning of a long process of political development in Iraq.

To ensure that another insurgent movement is unable to seize large swaths of Iraqi territory in the same manner as the Islamic State group, it would be wise for the United States to establish a long-term program to build and maintain the capacity of the Iraqi security forces. Over the next few decades, such a program can provide the breathing room necessary for Iraqis to construct — in fits and starts — a stable political order.

Brad Stapleton is a Visiting Research Fellow in Defense and Foreign Policy Studies at the Cato Institute. Send comments to [email protected].