Opinion writer

The day after President Trump announced, contrary to the advice of military and civilian advisers, that the United States would withdraw all troops immediately from Syria, Defense Secretary Jim Mattis announced his “retirement” — or, in the vernacular, that he was quitting. His resignation letter included a not-so-subtle rebuke of Trump. He wrote:

One core belief I have always held is that our strength as a nation is inextricably linked to the strength of our unique and comprehensive system of alliances and partnerships.

While the U.S. remains the indispensable nation in the free world, we cannot protect our interests or serve that role effectively without maintaining strong alliances and showing respect to those allies.

He made clear that on basic principles of foreign policy, Trump did not agree. “It is clear that China and Russia, for example, want to shape a world consistent with their authoritarian model — gaining veto authority over other nations' economic, diplomatic, and security decisions — to promote their own interests at the expense of their neighbors. That is why we must use all the tools of American power to provide for the common defense.”

The departure of the last “adult in the room” at a time when Trump is increasingly isolated, irrational and erratic will rightly frighten lawmakers and allies.

Mattis’s departure serves to underscore the utter lack of responsibility among Republicans who cheered on Trump with the pretense that others would restrain him. There is only one president, and ours is utterly unfit to serve.

I would suggest that three bipartisan steps are essential.

First, Mattis and other former national security officials should testify in open hearings in the House next year to lay out their concerns about Trump’s fitness and threat to national security. If they have not already done so, they should lay out their concerns to the special counsel about Trump’s reflexive support for Russian objectives.

Second, Congress must reassert its sole authority to wage war, denying Trump the legitimacy to unilaterally launch first strikes. In addition, it is essential to subpoena the translator’s notes from Helsinki to determine what, if any, pledges Trump made to Russian President Vladimir Putin.

Finally, it is time for Senate Republicans to seriously consider removing Trump in the event the House moves to impeach. Trump is a menace to our democracy and national security; unless and until Republicans recognize this and express a willingness to remove him, Trump may do untold damage during the time he has left in office. Supporting his reelection is entirely out of the question.

We are in uncharted territory, made more precarious by Republicans’ cowardice. If nothing else, perhaps Mattis’s departure will shock them into action.

Read more:

Carl Bildt: Mattis’s resignation spells a bumpy road ahead for Europe

Henry Olsen: Trump is now forging foreign policy on his own. Where will he take us?

Hugh Hewitt: In withdrawing from Syria, Trump makes a major error

Marc Thiessen: Our enemies are cheering Trump’s Syria decision. But it’s not too late.

Josh Rogin: Trump is leaving 50,000 Syrian civilians to die