Tuesday was the first time Waltz faced lawmakers since mistakenly adding a journalist to a private Signal chat used to discuss sensitive military plans.
The Pentagon has acknowledged that an Iranian ballistic missile hit Al Udeid Air Base in June during an Iranian attack after Trump downplayed the assault.
Opinion: The appropriate medal for troops who participated in the strikes on Iranian nuclear sites is not the one a Texas congressman recently proposed.
President Trump ordered U.S. forces to strike three key Iranian nuclear sites in June, a decision the Israeli leader says warrants a Nobel Peace Prize.