Around two dozen National Football League players knelt while the American national anthem played at Wembley Stadium in London, defying Donald Trump after he suggested players who take a knee during the anthem should be fired.
The outrage kicked off on Friday night, after Trump made a series of comments during a speech at a rally in Alabama.
"Wouldn't you love to see one of these NFL owners, when somebody disrespects our flag, to say, 'Get that son of a bitches off the field right now. Out! He's fired. He's fired!" said Trump.
In the rally, Trump referenced the growing trend of players taking a knee during the national anthem, which first began in 2016 by ex-San Francisco 49ers quarterback Colin Kaepernick in a statement aimed against police brutality.
Trump continued: "You know, some owner is going to do that. He's going to say, 'That guy that disrespects our flag, he's fired.' And that owner, they don't know it [but] they'll be the most popular person in this country."
The president then followed up his inflammatory words with a series of tweets over the weekend and seemingly uninvited the NBA champion Stephen Curry from the traditional White House visit for league victors.
The reaction from the nation's top athletes was instantaneous: LeBron James called the president a "bum" and, hours later, Major League Baseball saw its first player take a knee during the national anthem.
The president then went further Sunday morning by telling fans to boycott games.
But the kneeling NFL players have courted a huge amount of support from A-listers across the nation. Dozens of stars, including Ellen DeGeneres and John Legend, took to social media to support the on-field demonstrations from NFL players.
Stevie Wonder showed solidarity by "taking a knee" at the 2017 Global Citizens Festival over the weekend. On stage at Central Park, the "Isn't She Lovely" singer said he was "taking a knee for America."
He went on: "But not just one knee, I'm taking both knees, both knees in prayer for our planet, our future, our leaders of the world and our globe–amen."
Actress Zendaya tweeted and Instagrammed several times on the issue.
And many other celebrities expressed their outrage:
John Legend also wrote a piece for Slate about why the NFL players' protests are patriotic, which you can read here.
Grey's Anatomy's Jesse Williams went on MSNBC to explain why taking a knee was so important, which he documented further through a series of Instagram posts: