And over the weekend we learned that the Trump administration was investigating the emails of as many as 130 current or retired senior State Department officials, focusing on messages they sent to Hillary Clinton’s private email account when she was secretary of state. The administration has informed these officials that unclassified emails they sent years ago have been retroactively categorized as classified, making the officials potentially guilty of security violations. This is a meanspirited attempt to embarrass government employees.

Morale at the State Department has plummeted following this barrage of attacks. Secretary of State Mike Pompeo owes it to the men and women of the department to stand up for their nonpartisan service and defend them from the president’s bullying and persecution. Unfortunately, Mr. Pompeo seems unlikely to do this. His heated criticism on Tuesday of three congressional committees that are looking to depose diplomats involved in our Ukraine policy is not the sort of “support” our diplomats need right now.

No modern president has been as dismissive and even contemptuous of the State Department as Mr. Trump. He clearly does not understand or value the department. He has tried to slash its budget, advocating it be cut by a third in 2017 and nearly a quarter in 2018, only to be blocked by a bipartisan coalition of Republicans and Democrats in the House and Senate. Unlike other presidents, Mr. Trump has not appointed senior career State Department officers to important positions in the White House.

Mr. Trump also has the stingiest record of any recent president when it comes to appointing career Foreign Service officers to ambassadorships. Since the Kennedy administration, presidents when naming ambassadors have adhered to a formula of about 70 percent career diplomats and 30 percent political appointees. Mr. Trump’s appointees among career diplomats amount to only about 55 percent of ambassadorships. Only one of the 28 prestigious assistant secretary positions at the State Department is filled by a career officer — the lowest ever.

Democrats and Republicans in Congress must act to protect the State Department and the Foreign Service from Mr. Trump’s overt attacks and implicit disregard. The House in its impeachment inquiry should reaffirm the need for the State Department to be in charge of our relations with foreign countries. It should also examine how private citizens like Mr. Giuliani may have encroached on or usurped those responsibilities. For its part, the Senate should demand that the president send for ambassadorial confirmation a substantially higher number of career officers.