For the past 17 years, the United States has maintained a military presence in Iraq. On Friday, Iraq’s prime minister asked the United States to send a delegation to discuss a mechanism for withdrawing U.S. troops. In response, the U.S. State Department said it was ready to “recommit to our strategic partnership — not to discuss troop withdrawal.”

More so than at any point since the rise of the Islamic State in 2014, foreign troop presence in Iraq is now in question. Iranian-backed militias and politicians want U.S. troops to leave to strengthen Iran’s influence, and many anti-government protesters, who have been filling Iraq’s streets for months, want both the United States and Iran out to overhaul the corrupt and sectarian political system set up after the U.S.-led invasion in 2003.

Analysts warn that this impasse will only strengthen the remnants of the Islamic State, which the United States says its troops are on the ground to combat. Friday’s back-and-forth between Washington and Baghdad came one week after the United States killed Iran’s top military strategist, Qasem Soleimani, in a drone strike in Iraq — a move that brought Iran and the United States to the brink of war and renewed calls for the removal of U.S. forces.

The United States has faced the drawdown debate before, and in 2011, President Barack Obama withdrew most U.S. troops, only to redeploy some starting in 2014 to fight the Islamic State. With withdrawal once again on the table, here’s a look at some crucial moments for U.S. troops in the course of America’s military presence in Iraq.