On February 27, 2021, U.S. Ambassador to the United Nations, Linda Thomas-Greenfield, made an official notification to the President of the United Nations Security Council of a targeted military strike in east Syria. The notification letter explained that the U.S. was acting in self-defense under Article 51 of the U.N. Charter, in response to "an escalating series of threats and attacks by [Iran-supported non-State militia groups]." As a result, the letter indicates that defensive U.S. military action was targeted at "a facility used by Iran-supported non-State militia groups that are responsible for recent attacks against U.S. personnel and are engaged in ongoing planning for future such attacks." The letter stated that the U.S. military strike was a "necessary and proportionate action . . . taken to defend U.S. personnel and to deter further attacks." The letter concludes with a statement that the U.S. "remains prepared to use necessary and proportionate force in self-defense to respond to future threats to the United States and Coalition forces."