That's the second withdrawal from a second presence, requested by the Iraqi government after the rise of ISIL.
> The United States completed its prior withdrawal of troops in December 2011, concluding the Iraq War.[9] In June 2014, the United States formed Combined Joint Task Force – Operation Inherent Resolve (CJTF-OIR) and re-intervened at the request of the Iraqi government due to the rise of the Islamic State of Iraq and the Levant (ISIL).
> On 9 December 2017, Iraq declared victory against ISIL, concluding the 2013–2017 War in Iraq and commencing the latest ISIL insurgency in Iraq.
Perhaps those troops should have been withdrawn for the second time in early 2018. Alas, it took place after messier circumstances.
> On 31 December 2019 through 1 January 2020, the United States Embassy in Baghdad was attacked in response to the airstrikes.[6] On 3 January 2020, the United States conducted an airstrike that killed Iranian Major General Qasem Soleimani and Kata'ib Hezbollah commander Abu Mahdi al-Muhandis.[6] Iraq protested that the airstrike violated their sovereignty.[13]
>
> In March 2020, the U.S.-led coalition, Combined Joint Task Force – Operation Inherent Resolve (CJTF–OIR), began transferring control over a number of military installations back to Iraqi security forces, citing developments in the multi-year mission against the Islamic State of Iraq and the Levant (ISIL).
Or perhaps the second withdrawal has never actually completed.
> In February 2021, NATO announced it would expand its mission to train Iraqi forces in their fight against ISIL,[14] partially reversing the U.S.-led troop withdrawals. In April 2021, U.S. Central Command stated that there were no plans for a total withdrawal of U.S. forces from Iraq, citing continued threats posed by the ISIL insurgency and Iran-backed militias.[3]
