What did Donald Trump do today?

He lost the military to a degree no commander-in-chief ever has before.

Secretary of Defense Mark Esper has come under heavy criticism in the last two days for his complicity in Trump's use of military forces against American citizens to facilitate a photo opportunity. 

In response, Esper took the almost unheard of step of publicly opposing Trump's plan to invoke the Insurrection Act, which would—debatably—allow Trump to send the U.S. military into states without the permission of state governors. (No state has requested them. Trump's photo op assault was only possible in Washington, D.C. because of its status as a federal district.)

Appearing before reporters today, Esper said, "The option to use active duty forces in a law enforcement role should only be used as a matter of last resort, and only in the most urgent and dire of situations. We are not in one of those situations now. I do not support invoking the Insurrection Act." 

Esper has also claimed he didn't know that Trump was planning to coordinate the assault on a lawful protest in Lafayette Park with his impromptu campaign photo opportunity immediately afterward.

At first light today, Trump appeared to be heeding the chorus of voices within the military establishment against treating lawful protestors as a threat requiring a military response. Word leaked out of the White House that Trump would walk back his threat to invoke the Insurrection Act. Active-duty military police and soldiers deployed from Fort Bragg were ordered to stand down and leave Washington, D.C.

But after Esper spoke, reporters were told that his comments were "not well received." A Trump spokesperson ominously refused to speculate about whether Esper would keep his job. And the order demilitarizing the nation's capitol was abruptly revoked. 

It is almost unheard of for a defense secretary to publicly contradict a president on military matters. But Esper wasn't the only one to do it today. Esper's immediate predecessor, Gen. James Mattis, also tore into Trump in a lengthy statement. It reads, in part:

Instructions given by the military departments to our troops before the Normandy invasion reminded soldiers that “The Nazi slogan for destroying us…was ‘Divide and Conquer.’ Our American answer is ‘In Union there is Strength.’” We must summon that unity to surmount this crisis—confident that we are better than our politics. 

Donald Trump is the first president in my lifetime who does not try to unite the American people—does not even pretend to try. Instead he tries to divide us. We are witnessing the consequences of three years of this deliberate effort. We are witnessing the consequences of three years without mature leadership. We can unite without him, drawing on the strengths inherent in our civil society. This will not be easy, as the past few days have shown, but we owe it to our fellow citizens; to past generations that bled to defend our promise; and to our children.

...We know that we are better than the abuse of executive authority that we witnessed in Lafayette Square. We must reject and hold accountable those in office who would make a mockery of our Constitution.

Mattis and Trump parted on bad terms, with the former general resigning over Trump's abandonment of the United States' Kurdish allies in Syria.

Why should I care about this?

• The United States military defends the Constitution, not the president's re-election campaign.

• American citizens exercising their First Amendment rights are not the enemy of the United States military.

• Deciding to do something only after someone responsible tells you not to is what angry toddlers do.

• It's bad if a president's own cabinet appointee compares him to Nazis.