The Pentagon statement said Mr. Miller thanked Mr. Maier for his service. But a senior U.S. official said relations were strained between Mr. Maier and Mr. Miller, a former Army Green Beret who later served in counterterrorism jobs at the Pentagon and the White House’s National Security Council before Mr. Trump picked him to replace Mr. Esper in the Pentagon’s top civilian job.
Mr. Maier, 44, an Air National Guard intelligence officer who has worked in counterterrorism jobs in Republican and Democratic administrations for two decades, declined to comment. He recently completed a 90-day reservist tour in Kuwait. His firing was reported earlier by CNN.
While Mr. Maier’s backers expressed dismay at the manner of his dismissal — summoned midday Monday by the White House liaison officer at the Pentagon, Joshua Whitehouse, and told to clear out that day — they also criticized the new Defense Department leadership for playing to Mr. Trump’s overly optimistic assessment of the Islamic State’s status. The officials spoke on condition of anonymity because they were not authorized to publicly discuss the situation.
When Mr. Miller announced last month that the United States would draw down to 2,500 troops in both Iraq and Afghanistan by Jan. 15, he trumpeted the demise of the Islamic State. “Thanks to our more than 80 partners in the Defeat-ISIS Coalition, we have destroyed the ISIS caliphate and will ensure they never again gain a foothold to attack our people,” Mr. Miller said in remarks on Nov. 17.
But two months earlier, in late September, while still in his previous job as director of the National Counterterrorism Center, Mr. Miller struck a more sobering note in testimony to a House committee: “ISIS has repeatedly demonstrated the ability to rebound from severe losses over the past six years by relying on a dedicated cadre of veteran midlevel commanders, extensive clandestine networks, and downturns in CT pressure to persevere,” referring to counterterrorism pressure.
Other counterterrorism officials estimate that the Islamic State, despite having lost its territorial control in Iraq and Syria, still has as many as 10,000 guerrilla fighters there, and maintains resilient affiliates across East and West Africa and Afghanistan.
“Chris is a straight-up pro,” Nicholas J. Rasmussen, a former director of the National Counterterrorism Center, said of Mr. Maier. “The idea this is justified because we’ve won the war against ISIS strains credulity.”