With those words, Alexander Vindman, an Army officer and Purple Heart recipient, sought to shut down Republican attacks on his credibility.
Republicans went after him, nonetheless.
Republican Rep. Chris Stewart called Vindman's uniform a good reminder of his military service but also questioned why Vindman felt it necessary to wear it rather than a suit.
He wanted to know, too, if Vindman always insisted on being referred to by military rank rather than "Mr." as he did in an exchange earlier with Rep. Devin Nunes, the committee's top Republican. In that moment, he corrected Nunes and asked to be called "Lt. Col. Vindman, please."
The committee attacks mirrored the combative approach of the White House, which used its official Twitter account to retweet attacks on Vindman, who continues to work at the White House.
Some Republican attacks struggled to land. After Rep. Jim Jordan suggested that Vindman's peers questioned his judgment, Vindman read from a glowing performance review that called him "brilliant" and "unflappable."
Other attacks, including from the White House's director of social media, sought to imply that Vindman, a naturalized American citizen who was a toddler when his family fled Ukraine, may have dual loyalties.
Under questioning from GOP impeachment counsel Steve Castor, Vindman revealed that he was offered three times the post of Ukraine's defense minister while attending Zelenskiy's inauguration, but "immediately dismissed these offers." He says he notified his chain of command and counterintelligence officials upon returning to the U.S.
Castor questioned whether that created the impression of a conflict, to which Vindman replied, "It's more important what my American chain of command thinks."