Trump’s appointment of a set of generals to cabinet and national security positions initially raised concerns about the militarization of civilian government. in fact, each general required a congressional waiver to serve in the executive branch. Trump appeared to make the selections out of a combination of admiration for military officers, a desire to project martial strength impossible from him with a Vietnam-era draft deferral, and for sheer presentation value.

“If I’m doing a movie, I pick you, general,” he told Mattis on the afternoon of his inauguration.

And with the exception of Michael Flynn—a short-term advisor who pleaded guilty to lying to the FBI and who awaits sentencing—three other generals serving various roles in the Trump Administration were often viewed as the “adults in the room.” With their military discipline and experience in managing staff and interacting with the highest levels of government, they often stood in sharp contrast to the multi-millionaires, billionaires, and campaign surrogates Trump appointed to most other key executive positions.

Soon, none of these “adults” will remain:

Secretary of Defense Jim Mattis, Retired Marine General, Former Head of U.S. Central Command

Mattis proffered his resignation on Dec. 20 after Trump abruptly decided to withdraw American troops from Syria, declaring the war against ISIS successful and complete. Though it didn’t offer any direct criticism of the president, Mattis’s resignation letter expressed a view of “alliances and partnerships” at odds with Trump’s erratic and shifting strategy. Also worth noting: The letter had no words of praise for the commander-in-chief, either.

Defense Secretary James Mattis has resigned. Here’s the letter: pic.twitter.com/e2PulyXpXZ

— Elizabeth Beals (McLaughlin) (@Elizabeth_McLau) December 20, 2018

Trump, taking the high road, offered strong praise for Mattis in a tweet: “General Jim Mattis will be retiring, with distinction, at the end of February, after having served my Administration as Secretary of Defense for the past two years.”

General Jim Mattis will be retiring, with distinction, at the end of February, after having served my Administration as Secretary of Defense for the past two years. During Jim’s tenure, tremendous progress has been made, especially with respect to the purchase of new fighting….

— Donald J. Trump (@realDonaldTrump) December 20, 2018

Another noteworthy fact: Mattis resigned, never using the word ‘retire’ in his letter.

Chief of Staff John Kelly, Retired Marine General, and Former Secretary of Homeland Security and Head of U.S. Southern Command

John Kelly received an appointment originally as the Secretary of Homeland Security, and oversaw a remarkable and unprepared-for immigration ban on Jan. 27, 2017, that tangled airports nationwide as it went into effect with people in the air or at border control. It led to mass protests. Kelly said just days later that the ban was implemented poorly. A more limited version of the ban ultimately went into effect in mid-2018.

Trump tapped Kelly as chief of staff in July 2017 when he unceremoniously pushed out Reince Priebus, a long-time Republican operative. Kelly was seen as a steadier and stronger influence to whom Trump had already turned for advice.

Kelly imposed order on the Oval Office and Trump’s schedule, shifting from a pell-mell system, in which people wandered in and out without appointments, sometimes during other meetings. Notably, he made sure the Oval Office door was generally closed. Kelly reportedly had constant friction with Trump’s daughter and son-in-law, Ivanka and Jared Kushner, who serve as advisers. Trump often used Kelly as a bag man to inform other officials they were fired.

On a routine basis for most of his tenure, anonymous sources said Kelly’s departure was imminent, either through resignation of his own volition or forced by Trump. This intensified when Kelly defended White House Staff Secretary Rob Porter, seen as an indispensable assistant to Trump, in the wake of accusations of domestic abuse.

As recently as July, it appeared Trump and Kelly had negotiated Kelly remaining in place through 2020—and potentially through 2024 were Trump elected to a second term. But then on Dec. 8, Kelly announced he would step down effective at the end of 2018.

National Security Adviser Michael Flynn, Retired Army Lt. General, Former Director of the Defense Intelligence Agency

Flynn was forced out of the Defense Intelligence Agency in 2014 by President Obama, reportedly for an abrasive management style. He ran a private consulting firm with his son briefly that accepted fees from Russian- and Turkish-connected companies.

He acted as a robust campaigner for Trump during the presidential campaign, often leading chants of “lock her up” against Hillary Clinton for alleged crimes in mishandling confidential data and other unsubstantiated claims.

Flynn accepted the position as national security adviser a few days after Trump’s successful election, but resigned under pressure 24 days into the administration when reports emerged that he had lied to Vice President Mike Pence about his communications with the Russian ambassador, which led Pence to make inaccurate public statements.

Flynn lied to the FBI during its investigation of his statements. He pleaded guilty in December 2017, and agreed to aid the special counsel investigation into Russian interference with the presidential election. On Dec. 18, a judge postponed sentencing Flynn pending further recommendations from the special counsel’s team on the extent of his cooperation.

National Security Adviser H.R. McMaster, Retired Army Lt. General

McMaster succeeded Flynn as national security advisor, and remained an active military officer during his time in that role. McMaster cleared the White House of many nationalist-oriented staffers brought in by Trump’s advisor, Steve Bannon. This led to calls for McMaster’s ouster not long after he started in the national-security role.

McMaster ultimately decided to leave this position as of April 2018, and retired from the military shortly thereafter.