On 20 October 2021, multiple projectiles struck the Al-Tanf U.S. military base in Syrian opposition controlled territory, where members of the CJTF-OIR were training a Free Syrian Army unit known as Maghaweir al-Thowra. Although no injuries were sustained, the attack was unusually heavy—seemingly a mix of drone and rocket systems, with as many as five munitions used. Both the FSA areas and CJTF-OIR areas of the base were attacked. The coalition confirmed that the attack involved “a UAS [i.e., drone] attack coupled with IDF," referring to "Indirect Fire using Rockets."