Former Secretary of Defense Mark Esper reportedly sent a memo to the White House earlier this month saying that the U.S. should not call back more troops from Afghanistan until certain conditions were met, according to CNN. Citing sources familiar with the memo, the outlet reported that Esper, U.S. Central Command leader Marine Gen. Kenneth McKenzie, and Gen. Austin Miller, the commander of NATO’s mission in Afghanistan, all recommended keeping America’s troop presence in the Middle Eastern country because certain conditions had not been met. Without those conditions, they were reportedly concerned about the possibility of alienating American allies, eroding the credibility of the U.S. on the global stage, and adversely impacting the Afghan military.

While it is not immediately clear what those unmet conditions were, CNN reported that others agreed with this assessment, including Chairman of the Joint Chiefs of Staff Gen. Mark Milley. According to the outlet, the memo is believed to be one of the main reasons why President Donald Trump fired Esper last week. The memo was first reported by The Washington Post. On Monday, CNN also reported that military commanders are anticipating that the outgoing president will give a final order—perhaps as soon as this week–about the withdrawal of troops from Afghanistan and Iraq before he leaves office in January.