This month marks twenty years since the United States invaded Iraq in 2003. The bloodshed that followed cost Iraq and America dearly. Yet there was a winner in the chaos: Iraq’s neighbor and rival Iran. The invasion removed Iraq as a check on Iran; Tehran no longer had to fear the nation that invaded it in 1980. Ever since, U.S. strategy in the Middle East has had to deal with the consequences of a more powerful Tehran. “U.S. forces,” said Secretary of Defense Lloyd Austin in Baghdad on March 7, “are ready to remain in Iraq.” Blocking Iran there and elsewhere has become a U.S. job that will never end. 

The invasion and the subsequent dismantling of the Iraqi state prompted lawlessness and the emergence of a new order rooted in violence, sectarianism, and corruption. A weak Iraq left the door open for Iranian influence. Tehran built militias and political movements within Iraq’s Shia majority and used these groups to target U.S. interests. The groups demanded a veto in Iraqi politics, using force when they didn’t get their way. 

The militias contributed to a sectarianization of politics and society that saw Baghdad segregate itself and religious minorities flee. Former Prime Minister Nouri al-Maliki’s own efforts to make the Iraqi military loyal to him alone contributed to its collapse against the Islamic State in 2014. An army that had received a decade of U.S. training and equipment abandoned Iraq’s second-largest city under pressure from a small band of lowlifes. 

ISIS’s rise (itself an aftershock of the Iraq invasion, which spawned ISIS predecessor Al Qaeda in Iraq) strengthened Iran’s hand further. As the Iraqi army failed, militias answered the call. Many of these militias were backed by Tehran. Efforts to integrate the militias into Iraq’s armed forces only bandaged the problem. These militias remain outside the state’s control, and have routinely shot rockets at the U.S. embassy and U.S. bases. In 2019, they stormed the Green Zone when the United States hit back. Counterbalancing these militias’ influence has become a major justification for the continued presence of thousands of U.S. troops in Iraq. Countering the militias is a mission that will never end. 

The militias also smuggle arms into Syria and Lebanon. These weapons have triggered an Israeli interdiction campaign that has been a headache for U.S. efforts in the region. The weapons flow contributes to the Israeli military’s warnings that its next war with Iran’s Lebanese ally Hezbollah will require a fast, aggressive air campaign that could have huge costs in Lebanon. U.S.-made bombs plunging into Beirut apartment blocks, even if aimed at Hezbollah bunkers below, will hurt America’s image in the region. And blocking the Iranian supply lines into the area has become a justification for keeping U.S. troops in Syria. Blocking roads our invasion opened is another mission that will never end.

The problems stretch beyond Iraq, Syria, and Lebanon. The Gulf states fear an Iran unchecked by Iraq and seek a security guarantor. America is their best choice. The Iraq War and the Global War on Terrorism drew a huge U.S. troop presence to their shores; fear of Iran, plus big Gulf investments in the U.S. policy and defense advisory sectors, have helped keep them there. Crises with Iran have seen deployments of scarce U.S. assets like Patriot missile batteries.

At bottom, the invasion reflected a shift in U.S. Middle East strategy away from seeking balance and towards seeking transformation. We thought a free Iraq would inspire a wave of democratization in the region. This did not happen. Worse, we now do the balancing ourselves, rather than relying on our enemies’ self-interest to do the balancing for us. And Washington’s policy sphere is reluctant to return to letting the region balance itself. Balancing Iran is another mission that will never end.

Last but not least are Iran’s nuclear and missile programs. Their current state—high levels of enrichment, multiple enrichment facilities, and a diverse array of short- and medium-range ballistic missiles—is inseparable from the Iraq War. Without Iraq to fear, Iran has more power to aim at the United States. Top U.S. worries like nuclear weapons and longer-range ballistic missiles are not good tools for Iran to counter a strong Iraqi state on its border. Conventional military power, backed by short-range ballistic missiles, would be far better suited for that task. Building these Iraq-focused capabilities would draw resources away from Iranian efforts to develop tools for fighting America and Israel. 

To be sure, some Iranian advances in short-range ballistic missiles aimed at Iraq would have also increased the Iranian threat to U.S. bases in the region. But those risks are not at the same scale as the Iranian nuclear and missile threat we face today. With Iran enriching uranium to near-weapons-grade purity, fears are growing that Israel may strike Tehran’s nuclear sites, a move that could spark a major war.

Of course, we cannot know what the Middle East would look like today if the United States had not gone into Iraq. Yet it’s hard to envision a pathway that would have seen a similar rise in Iranian power. Invading Iraq brought many evils, but our long confrontation with Iran—one that may yet yield war—is one of the most enduring. 

John Allen Gay is executive director of the John Quincy Adams Society and coauthor of War With Iran: Political, Military, and Economic Consequences.

Image: Shutterstock.