On December 13, the WH announced Trump’s intent to nominate retired U.S. Colonel Andrea L. Thompson to be the Under Secretary of State for Arms Control and International Security (State/T).  She was confirmed by the U.S. Senate by voice vote on April 26, 2018.  She succeeded Rose Eileen Gottemoeller who served from 2014–2016, and was subsequently appointed to NATO (see Rose @Gottemoeller Moves to @NATO as First Female Deputy Secretary General).  More about Thompson here.

On September 20, about 17 months into her tenure, Secretary Pompeo announced Thompson’s departure without detailing the reason she is leaving one of the top senior jobs in Foggy Bottom. So the T bureau is once more vacant, as well as the Bureau of Arms Control, Verification and Compliance which does not have a Senate-confirmed assistant secretary as of this writing (office is currently headed by Thomas DiNanno as Senior Bureau Official and Deputy Assistant Secretary of State for Defense Policy, Emerging Threats, and Outreach). The Bureau of International Security and Nonproliferation, and the Bureau of Political-Military Affairs both have Senate-confirmed assistant secretaries, presumably one of them would be up as Acting “T” until a a new nominee is identified and confirmed. How long that would take, that’s a guessing game we all can play while chaos marches on.

Related post:

• State/T to SFRC in Full Swagger and Smirk, “You’ll have to ask Russia” May 2019
• Confirmations: Grenell, Hushek, Thompson, Poblete, Madison, and 5 FS Lists April 2018
• Andrea L. Thompson to be Under Secretary for Arms Control and International Security (T)Dec 2017

Under Sec for Arms Control at ⁦@StateDept⁩, Andrea Thompson, departing after allegations that Maria Butina attended her wedding. Butina’s boyfriend at the time officiated her wedding which took place before FBI investigation into Butina & also before Thompson conf hearing. pic.twitter.com/HC2nOB1cRY

— Kylie Atwood (@kylieatwood) September 20, 2019

State Department announces the departure of Andrea Thompson, former national security adviser to Pence. pic.twitter.com/PI9ztwHaOq

— Olivier Knox (@OKnox) September 20, 2019

Thank you @SecPompeo for the opportunity to lead this incredible team. It’s been an honor to serve our great Nation for almost 3 yrs @WhiteHouse & @StateDept. I’m so very proud of our T Family team & what we’ve accomplished together for our Nation’s security. 🇺🇸 https://t.co/7vQnzeJbvZ

— U/S of State Andrea Thompson (@UnderSecT) September 20, 2019

Thrilled to host a Women in National Security (WiNS) lunch w/ this esteemed group of Ambassadors, Embassy officials, & private sector leaders. Great insights. Engaging discussion on issues of nat'l and int'l security & mentoring the next generation of national security leaders. pic.twitter.com/0Jv882iCVJ

— U/S of State Andrea Thompson (@UnderSecT) September 19, 2019

Pompeo sent his deputy to lead talks with Russia this week, at the last minute, instead of Undersecretary of State for Arms Control Andrea Thompson amidst continuing concern over her failure to disclose ties with Paul Erickson, boyfriend of Maria Butina – https://t.co/fc7BEnypCG

— Eliana Johnson (@elianayjohnson) July 17, 2019

Fire from Bob Menendez when he asks Undersecretary of State for Arms Control Andrea Thompson about Russian nuclear plans without New START.

Thompson: "It's a good question for Russia, senator."
…
Menendez: "I’m not asking Russia about our national defense. I'm asking you." pic.twitter.com/v3i0VXMhIr

— Kyle Griffin (@kylegriffin1) May 15, 2019