The Democratic chairs of the House Oversight and House Foreign Affairs committees announced subpoenas Monday for four State Department officials as part of their investigation into the firing of former Inspector General Steve Linick.

Why it matters: The two committees, in addition to Democrats on the Senate Foreign Relations Committee, are investigating whether Linick was fired because he was probing Secretary of State Mike Pompeo and the State Department's attempts to bypass Congress to sell weapons to Saudi Arabia and the United Arab Emirates.

Details: The subpoenas seek to compel depositions from Under Secretary Brian Bulatao, Legal Adviser Marik String, Deputy Assistant Secretary for Political-Military Affairs Michael Miller, and senior adviser Toni Porter.

The big picture: Linick told Congress in June he was conducting five investigations into Pompeo and the State Department before he was fired by Trump at Pompeo's recommendation.

• Linick testified that Bulatao, a longtime aide to Pompeo, "tried to bully" him into dropping his investigation into the arms sales.
• Linick was also probing allegations of misuse of staff by Pompeo — an investigation that Pompeo claims he was unaware of.

The other side: Pompeo has said Linick"wasn’t performing a function in a way that we had tried to get him to" and has asked for an investigation into Linick and a "disturbing pattern of leaks." He has denied wrongdoing.

What they're saying: House Foreign Affairs chair Eliot Engel (D-N.Y.), House Oversight chair Carolyn Maloney (D-N.Y.) and Senate Foreign Relations ranking member Bob Menendez (D-N.J.) revealed that former State Department official Charles Faulkner voluntarily testified about Linick's removal on June 24.

• “Mr. Faulkner’s testimony depicts a small group of senior State Department officials determined to ignore legitimate humanitarian concerns among their ranks and on Capitol Hill in order to ram through more than $8 billion in arms sales to Gulf countries," the chairs wrote in a press release.
• "Mr. Faulkner testified that Congress had “legitimate” concerns when it was holding up these sales on humanitarian grounds and that State Department officials weren’t surprised by the Saudis’ reckless use of U.S.-built weapons and the resulting loss of innocent life."
• "Nevertheless, the Department’s senior leadership appeared determined to see the sales go forward."

Go deeper: Pompeo says he wasn't aware ousted inspector general was investigating him