After he attacked the parents of a Muslim American soldier killed in Iraq, Donald Trump reportedly had to ask what a Gold Star family was.

Khizr and Ghazala Khan, the parents of Capt. Humayun Khan, a soldier who died while protecting his unit in 2004, appeared at the Democratic National Convention in July, after the GOP presidential nominee had attacked Muslims. Trump responded to the stirring speech Khizr Khan gave by suggesting that the soldier’s mother had not been allowed to speak on stage because she’s a Muslim. Ghazala Khan said she did not speak because she was too upset.

New York Magazine’s Gabriel Sherman reported on Saturday that when one adviser warned Trump he had just attacked a Gold Star family, the GOP nominee responded “what’s that?” The term is commonly used to refer to any family that has lost a loved one in war. The United States has officially recognized these families since 1936.

Trump has pledged to support veterans throughout his campaign. Earlier this year, he promised to donate millions to veterans groups, but only appeared to do so months later after The Washington Post noted that he had not fulfilled his promise.

Sherman also reported that Paul Manafort, who was then Trump’s campaign chairman, had to explain what ‘Gold Star family’ meant.

“The election is about the American people, it’s not about you,” Manafort reportedly said, adding that Khizr Khan wasn’t running for president.

Khan held up a pocket copy of the constitution at the Democrats’ convention and asked Trump if he had even read it and what sacrifices he had made for the country. The Gold Star father has pleaded with GOP leaders to repudiate Trump and appeared in a moving ad for Democratic presidential candidate Hillary Clinton this month.

Editor’s note: Donald Trump regularly incites political violence and is a serial liar, rampant xenophobe, racist, misogynist and birther who has repeatedly pledged to ban all Muslims — 1.6 billion members of an entire religion — from entering the U.S.