The principal focus of the House impeachment inquiry is President Donald Trump and his attempts to pressure Ukraine to investigate a potential political rival. What has come into sharper focus in the first days of public testimony is the professionalism of the country’s diplomatic corps and the lengths to which the president has gone to attack the quality and value of that service.

With threats, intimidation and indifference, the president has sought to undermine career Foreign Service officers who have served through Republican and Democratic administrations. Through notable lack of support from Secretary of State Mike Pompeo when his career officials have come under fire, the administration has contributed to a decline in morale and an exodus within the ranks that have longer-term consequences.

As if on cue, on Friday morning, Trump offered a real-time example of these efforts. It came as former Ukraine Ambassador Marie Yovanovitch was testifying before the House Intelligence Committee about the circumstances of her abrupt dismissal by the president in the spring.

In the middle of that hearing, Trump tweeted a fresh attack against her. “Everywhere Marie Yovanovitch went turned bad,” he tweeted. He went on to name places she had served, difficult, challenging and at times dangerous assignments. He ended by stating, “It is a U.S. President’s absolute right to appoint ambassadors.”

Yovanovitch’s appearance on Friday followed testimony on Wednesday by two other career diplomats: William Taylor, who is serving as the senior diplomat in Ukraine, and George Kent, the State Department’s leading expert on Ukraine. None was there as a public advocate for or against the impeachment of the president but as what Taylor described as “fact” witnesses to events under examination.

They were measured and direct as they recounted what they had seen and heard from their individual vantage points, resisting efforts to be drawn into the political warfare being waged between Republicans and Democrats on the committee while remaining focused on providing a narrative of the events of which they were a part, based on recollections, notes and memos.

But they were also passionate in describing the alarm they felt about what they regarded as the hijacking of U.S. policy, and the traditional policy process, by Rudy Giuliani, the president’s personal attorney, which they saw as a subversion of U.S. interests for personal or political interests.

They were even more clear about their dismay with what they saw as the president’s determination to make military aid to Ukraine and a White House meeting with Volodymyr Zelensky, the newly elected president, contingent on a public pronouncement of investigations into Ukraine’s alleged role in the 2016 election and into former Vice President Joe Biden and his son Hunter, who served on the board of a Ukrainian energy company.

Yovanovitch, Taylor, Kent and thousands and thousands like them have served loyally throughout the government for generations. Mostly they have little public visibility, preferring to avoid the limelight. But things have changed. Now as never since perhaps the McCarthy era of the 1950s, they are under attack for doing what they long have done.

Yovanovitch described the impact. “The attacks,” she said, “are leading to a crisis in the State Department as the policy process is visibly unraveling.” She said the crisis is much broader than the impact on the lives of individual career officials. “The State Department,” she said, “is being hollowed out from within at a competitive and complex time on the world stage.”

In some of her most pointed comments of the morning, she put the leadership of the department on notice. “This is not a time to undercut our diplomats,” she said. “It is the responsibility of the department’s leaders to stand up for the institution and the individuals who make that institution, still, today, the most effective diplomatic force in the world.”

The deterioration at the State Department predated Pompeo’s arrival. Under Rex Tillerson, Trump’s first secretary of state, departmental morale began to sink, in part because he seemed unwilling to defend against drastic budget cuts proposed at the start of the administration.

Pompeo’s arrival, after Tillerson was sacked by a presidential tweet, brought a moment of hope to the department. But over time, things have gotten worse, and as the Ukraine issue erupted into public view, Pompeo’s silence has been especially notable. That is the difficulty of serving a president who demands loyalty to him and often to him alone.