Flynn's military career included a key role in shaping U.S. counterterrorism strategy and dismantling insurgent networks in Afghanistan and Iraq, and he was given numerous combat arms, conventional, and special operations senior intelligence assignments.[2][3][4] He served as the 18th Director of the Defense Intelligence Agency, serving from July 2012 until his forced retirement from the military in August 2014
Flynn recounted that his agency was producing intelligence reports indicating that radical Islamists were the main force in the Syrian insurgency and "that Turkey was looking the other way when it came to the growth of the Islamic State inside Syria". According to Flynn, these reports "got enormous pushback from the Obama administration," who he felt "did not want to hear the truth". According to former DIA official W. Patrick Lang: "Flynn incurred the wrath of the White House by insisting on telling the truth about Syria … they shoved him out. He wouldn't shut up."[43]