National Security Council (NSC) official Alexander Vindman showed up to testify Tuesday as part of the Democrats’ closed-door impeachment inquiry into President Trump in full military uniform.

This is despite not wearing one to work every day at the NSC, according to several sources.

Although Vindman is a lieutenant colonel in the U.S. Army, he is serving an assignment at the NSC as the director for European Affairs. According to sources at the NSC, Vindman does not wear his uniform to work at the NSC, where the standard dress is business wear.

One source said he donned the uniform “for show.” The source pointed out that Vindman was ironically wearing a presidential service badge on his uniform — as he testifies on how he went with his twin brother, a lawyer at the NSC, with concerns about Trump’s handling of Ukraine foreign policy and his personal lawyer, Rudy Giuliani, investigating Joe Biden and his son for corruption.

Vindman’s opening statement leaked to the New York Times the night before his testimony showed he was concerned that Ukraine helping investigate Biden would jeopardize bipartisan support for Ukraine.

According to the Times, Vindman, who was born in Ukraine and is fluent in Ukrainian and Russia, may have served as an informal adviser to Ukrainian officials looking for advice on how to deal with Rudy Giuliani’s efforts to investigate corruption by Joe Biden and his son Hunter Biden.

According to the paper: “His heritage gave Colonel Vindman, who is fluent in both Ukrainian and Russian, unique insight into Mr. Trump’s pressure campaign; on numerous occasions, Ukrainian officials sought him out for advice about how to deal with Mr. Giuliani.”

John Yoo, a former Bush administration Justice Department official, said Monday evening on Fox News’ “Ingraham Angle” that he found it “astounding” that Vindman would be advising Ukrainian officials against Trump’s interests.

“You know, some people might call that espionage,” Yoo said.

Some mainstream media journalists drew a contrast between Vindman in “full uniform” with those, like Yoo, who questioned Vindman’s loyalty to the U.S.