Donald Trump's latest fight sees him taking on many of the players of America's most beloved sport.
NFL teams staged a show of solidarity with protesting players before Sunday's games by kneeling, linking arms or staying off the field during the U.S. national anthem, defying President Donald Trump's call for owners to fire those who refuse to stand.
Here's why it has become the most talked about issue in the US this weekend.
Anthem protests of one sort or another began with former San Francisco 49ers quarterback Colin Kaepernick over 12 months ago in the pre-season to the 2016 NFL campaign.
Kaepernick sat down for the anthem before a game against the Green Bay Packers (it was subsequently discovered he had done the same in two earlier pre-season games but the fact had gone unreported) and when asked afterwards about his decision, Kaepernick said: "I am not going to stand up to show pride in a flag for a country that oppresses black people and people of color.
"To me, this is bigger than football and it would be selfish on my part to look the other way. There are bodies in the street and people getting paid leave and getting away with murder."
After Kaepernick's protest was highlighted in the media, the following week he and team-mate Eric Reid kneeled during the anthem before a game against San Diego.
Kaepernick's and Reid decided to kneel rather than sit after a chat with former Green Beret Nate Boyer, feeling that by 'taking a knee' they could make their protest while still being respectful to the anthem.
Kaepernick continued his kneeling protest before every game of the 2016 season before parting ways with the 49ers. None of the 32 teams in the NFL have offered him a job since, which has led to accusations that he has been effectively 'blacklisted' by NFL owners. Others argue that he is simply not good enough to merit a spot on a roster but his career stats, play-off record and age make that a hotly debated topic in the US.
The original protest by Kaepernick and other NFL players began during the 2016 Presidential campaign. Shortly after the media storm blew up around the issue, Trump suggested Kaepernick should "find a country that works better for him".
In October 2016 Trump blamed the NFL's falling ratings on Kaepernick but he really took his condemnation of protesting players up to new heights this weekend.
At a rally in Alabama, Trump said: “Wouldn’t you love to see one of these NFL owners, when somebody disrespects our flag, to say, ‘Get that son of a bitch off the field right now. Out! He’s fired. He’s fired!’”
“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.”
NFL commissioner Roger Goodell hit back, saying: “The NFL and our players are at our best when we help create a sense of unity in our country and our culture,” Goodell said. “Divisive comments like these demonstrate an unfortunate lack of respect for the NFL, our great game and all of our players, and a failure to understand the overwhelming force for good our clubs and players represent in our communities.”
A number of players also issued personal responses to Trump's speech.
Jacksonville Jaguar owner Shahid Khan, who contributed personally to Trump's inaugural committee, joined the players in protests before this weekend's game in London.
Some teams, such as the Tennessee Titans and the Seattle Seahawks, stayed in the lockerroom and refused to enter the field until the anthem was over.
In Detroit, several members of the Lions knelt while singer Rico Lavelle dropped to one knee and pumped a fist in the air at the end of his performance of the "Star-Spangled Banner."
In Philadelphia, city police officers joined with Eagles and New York Giants players and Eagles team owner Jeffrey Lurie to link arms during the anthem in a sign of solidarity.
This issue is not going to go away and if we know anything about Trump, he will continue to fan the flames on social media.
Last night he tweeted about it again while a number of games were underway
Tonight the Arizona Cardinals play the Dallas Cowboys but Cowboys coach Jason Garrett has already said he does not expect his players to join the protest.
However the protests are spreading.
Already the first Major League Baseball player to 'take a knee' has happened as Oakland A's catcher Bruce Maxwell kneeled during the anthem before a game against Texas.
Before Game 1 of the Women's NBA Finals over the weekend the Los Angeles Sparks left the court during the anthem while the Minnesota Lynx linked arms.
Meanwhile a host of the NBA's biggest stars, led by LeBron James, have fired back at Trump over his comments this weekend about not meeting the champion Golden State Warriors because of star player Steph Curry's 'hesitation' to visit the White House.
U bum @StephenCurry30 already said he ain't going! So therefore ain't no invite. Going to White House was a great honor until you showed up!— LeBron James (@KingJames) September 23, 2017
As we have seen from Hillary Clinton to North Korea, Trump loves to create conflict and by hitting on the twin subjects of patriotism and American Football he has struck controversy gold.
With the NFL season barely three weeks old, the baseball season heading towards the World Series and the NBA season not even started yet, this one is going to run and run.