Just a few days ago, acting defense secretary Patrick Shanahan was quietly campaigning to be formally nominated to his post. In a story published Friday, Politico reported that he made “more than two dozen trips to Capitol Hill in the past few months to win over lawmakers,” enlisted “the support of national security leaders in both parties” and made the case to Politico reporters “that he is an effective steward of the military — one who knows how to deal with the Trump decision-making style that has flummoxed so many past Cabinet members.”

Then, on Tuesday afternoon, President Trump abruptly announced that Shanahan “has decided not to go forward with his confirmation process so that he can devote more time to his family.” It is hard to know whether this banal cliche was repeated mindlessly or cruelly. For it soon emerged that Shanahan’s family was the reason he is not only pulling out of consideration to become secretary of defense but leaving the Defense Department altogether.

Various news outlets have reported allegations of domestic abuse arising from the dissolution of Shanahan’s marriage a decade ago. His then-wife accused him of assaulting her; he accused her of assaulting him. Based on the fact that the police arrested his wife, it would seem he had the stronger case. Even more horrifying was that, as The Post reported, Shanahan’s son was arrested in 2011 for a brutal baseball-bat attack on his mother, Shanahan’s ex-wife, which left “her unconscious in a pool of blood, her skull fractured and with internal injuries that required surgery.” This was not, of course, Shanahan’s fault — but he did defend his son by claiming he acted in self-defense.

Even such loyalty to his son can be forgivable. Less forgivable is the possibility that the administration concealed this incident from the Senate when Shanahan was confirmed for deputy secretary of defense — as members and staff of the Senate Armed Services Committee now say. That Shanahan’s FBI clearance process to be nominated for defense secretary was dragging along gives credence to the supposition that this domestic-violence incident had not been fully dealt with during Shanahan’s earlier confirmation. The kind of vetting that was automatic in past administrations is unknown in this one.

So now the Defense Department is led by a new acting secretary, Army Secretary Mark Esper. Unlike Shanahan, Esper at least has military experience, and he has previously worked both as a congressional staffer and a Pentagon official. But like Shanahan, he comes out of the defense industry, so conflicts of interest abound. This is diversity, Trump style: replacing a former Boeing executive with a former Raytheon executive.

Having no confirmed defense secretary for six months would be anomalous in any other administration, but it’s par for the course in this one. There is more “acting” in Washington than Hollywood these days. As my colleague Philip Bump has noted, “more than a fifth of Trump’s presidency has seen departments run by acting heads.” Trump has said he likes “acting” officials because “It gives me more flexibility.” What he really means is that acting officials are unlikely to challenge him. When he says jump, they ask, “How high?”

Shanahan was a perfect example. As Politico reported: “Five current and former Defense Department officials who have worked directly with Shanahan, both uniformed and civilian, say the acting secretary is too easily manipulated by an unpredictable White House. These people say that in his six months of running the Pentagon, Shanahan has shown markedly less independence than former Defense Secretary Jim Mattis, a retired four-star general who slow-walked or outright resisted Trump’s policies on issues such as Syria strategy, transgender troops and the sending of military units to the U.S.-Mexico border. Shanahan, they say, is out of his league, outgunned by others in Trump’s orbit and so eager to get the job that he fails to defend the Pentagon’s position.”

Presumably, Esper will be just as eager to curry favor with the president. The way things are going, Trump need never confirm another defense secretary again; he can just appoint one acting secretary after another.

But while Trump appreciates Cabinet members who do not check his erratic impulses, America’s national security is not served by having yes-men or yes-women in senior positions of responsibility. Note that the crisis, which is drawing the United States and Iran to the brink of hostilities, did not start in earnest until after Mattis had left the Pentagon. Mattis had been a brake on Trump; Shanahan was an enabler.

That the Defense Department is leaderless as the United States is embroiled in a national security crisis is symptomatic of the chaos that has engulfed the government from day one of the Trump administration. Most administrations function more smoothly with the passage of time because the president learns on the job and weeds out dud appointees. In this administration, the dynamic is reversed: Trump becomes more willful and erratic the longer he stays in office. Rather than strengthening his team, he weakens it by replacing appointees who display independence of judgment with sycophants who will affirm his greatness on command.

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