Players from several NFL teams peacefully protested President Trump's recent comments during the national anthem on game day Sunday, Sept. 24. (Amber Ferguson/The Washington Post)

Some stood. Some kneeled. Some remained in the locker room, choosing to speak through their absence from the NFL’s pregame ceremonies, in which the American flag is displayed and the national anthem sung.

But from London to Los Angeles, virtually all NFL players on the sidelines before kickoff of Sunday’s slate of 14 games locked arms with each other in response to President Trump’s three-day campaign demanding that team owners “fire or suspend” players who kneel during the national anthem and calling on fans to boycott games if the form of protest continued.

The silent rebuke to the president, determined independently by each of the 28 NFL teams in action Sunday, represented an unprecedented collective action and show of solidarity among players who battle one another for at least 16 weeks each season.

Some, such as the Jacksonville Jaguars, Philadelphia Eagles and Washington Redskins, were joined on the sideline by their team owners, Shahid Khan, Jeffrey Lurie and Daniel Snyder, respectively. Most were joined in standing shoulder-to-shoulder by coaches, staff and, in some cases, police officers.

All but two of the NFL’s 32 team owners and CEOs issued statements Saturday night and through Sunday in response to Trump’s crusade against protesting NFL players, which began in earnest during a rally Friday night in Alabama. After making a thinly veiled allusion to former San Francisco 49ers quarterback Colin Kaepernick, who sparked a national debate by taking a knee before August 2016 preseason games to protest police violence against minorities, Trump called on NFL coaches to get the “son of a bitch” players off the field if they continued to kneel. The president repeated his call with no less intensity on Twitter on Saturday and Sunday morning.

After players of several NFL teams kneeled, locked arms or stayed in their locker rooms during the national anthem on Sept. 24, President Trump said his criticism of the protests “has nothing to do with race.” (Bastien Inzaurralde/The Washington Post)

On Monday, Trump took another shot at the league. In a series of tweets, Trump derided the players who took a knee and said it displayed scorn for “our Country, Flag and National Anthem.”

“NFL must respect this!” he wrote.

Many people booed the players who kneeled yesterday (which was a small percentage of total),” Trump wrote in a separate tweet. “These are fans who demand respect for our Flag!”

The tenor and substance of those remarks, along with criticism that NFL rule changes for safety’s sake had made the game boring, triggered reactions from many players, coaches and executives. While far from universally in favor of Kaepernick’s method of protest, many owners issued statements defending the rights of players — and all Americans — to express themselves on matters they are passionate about.

Among the more notable was New England Patriots owner Robert Kraft, a vocal Trump supporter and a $1 million donor to his inaugural.

President Trump called on NFL owners to fire players who kneel during the national anthem, during a rambling speech in Alabama Sept. 22. (Victoria Walker/The Washington Post)

“There is no greater unifier in this country than sports and, unfortunately, nothing more divisive than politics,” Kraft wrote in his statement released Sunday morning. “I think our political leaders could learn a lot from the lessons of teamwork and the importance of working together toward a common goal.”

Snyder was among those who had remained silent during the day Sunday, but the team issued a statement close to the 8:30 p.m. kickoff at FedEx Field.

“Football has always served as the great unifier, bringing people together to celebrate the values of courage, commitment and achievement,” the statement read. “We are proud of the players, coaches and fans of the Washington Redskins for all that they have done to improve the lives of others in neighborhoods all across our region.

“We are also grateful for the sacrifices made by the brave men and women of our armed forces that have provided us the freedom to play football. In that great tradition, the Washington Redskins will work to address divisions and bring unity, civility and respect to our greater community.”

NFL game day began at London’s Wembley Stadium, where the Baltimore Ravens and Jaguars kicked off at 9:30 a.m. ET, following two early-morning tweets in which Trump reiterated his objections to anthem protesters and seemed to encourage fans who agreed with him to stop attending games.

Before the morning’s first game, Ravens and Jaguars players and coaches locked arms on the sideline — some kneeling, others standing — as the anthem played. It was a scene repeated in 13 other stadiums stateside, from Gillette Stadium in Foxborough, Mass., to StubHub Center in the Los Angeles suburbs.

Trump reacted to the showings by tweeting at 2:20 p.m.: “Great solidarity for our National Anthem and for our Country. Standing with locked arms is good, kneeling is not acceptable. Bad ratings!”

Some NFL fans agreed with the president. At Foxborough, some booed the gestures while others chanted, “Stand up.” Similar dissent was heard in Buffalo, where boos rained down from some segments of the stadium as members of the Denver Broncos took knees.

Just about the time the NFL’s 4 p.m. games were kicking off, Trump addressed the matter with reporters as he left Bedminster, N.J. “I think the owners should do something about it. It’s very disrespectful to our flag and our country.”

He bristled at the suggestion that his comments had inflamed racial tensions, saying: “I’ve never said anything about race. This has nothing to do with race or anything else. This has to do with respect for our country, and respect for our flag.”

He also denied that he wants his supporters to boycott the NFL.

“No, no, no — I don’t,” Trump told reporters after returning to the White House on Sunday evening. “They can do whatever they want.”

However, the nonprofit group America First Policies launched a Facebook ad Sunday urging supporters to stand with the president by turning off NFL games. The online ad features an image of Trump with his hand over his heart and the hashtag ­“#TakeAStandNotAKnee.”

It was Trump’s campaign-style rhetoric that gave new life to what had become an isolated, almost passe form of protest. Speaking to supporters in Alabama on Friday night, he decried Kaepernick and later assailed rules meant to improve player safety, saying they hurt the game’s entertainment value and pointing to declining television ratings for NFL games.

In closed-door meetings Saturday night, many NFL players and coaches discussed whether and how to respond as the national anthem played before Sunday’s kickoffs, with individual teams determining their own approaches.

During pregame warm-ups before Miami faced the Jets, Dolphins running back Jay Ajayi sported an “#I’mWithKap” T-shirt.

The Pittsburgh Steelers chose to remain in the locker room during the playing of the national anthem before their 1 p.m. kickoff in Chicago, while Coach Mike Tomlin took the field with several assistants and left tackle Alejandro Villanueva, a former Army Ranger, stood just outside the locker room tunnel. The Seattle Seahawks chose a similar course, with players issuing a joint statement that read in part: “We will not stand for the injustice that has plagued people of color in this country. Out of love for our country and in honor of the sacrifices made on our behalf, we unite to oppose those that would deny our most basic freedoms.”

Before kickoff of the New York Giants’ game in Philadelphia, as an enormous American flag was stretched over the field, Lurie, the Eagles’ owner, joined his players, staff and several police officers standing to shoulder to shoulder on the team’s sideline. Eagles safety Malcolm Jenkins, standing near Lurie, raised his fist. Some Giants, such as Olivier Vernon, Landon Collins and Damon Harrison, kneeled while others stood — each extending an arm to the man beside him.

Afterward, Giants wide receiver Brandon Marshall said: “It’s getting to the point right now in America where we can’t ignore what’s going on. This is real. . . .

“What Kaepernick has done, he really started a conversation,” Marshall continued. “He’s galvanized the community to really sit down and really look at themselves and see how we contribute to it and how we can be a solution moving forward. I’m really disappointed in President Trump’s remarks. That just proves: This is the most powerful man in the country, and for him to stand up and say that shows what we feel is real. That’s what we’re saying. Exactly how he talks, that’s what we’re talking about.”

During pregame ceremonies at FedEx Field on Sunday night, boos rained from several sections of the stands at the sight of most Oakland Raiders players and five Redskins declining to stand for the anthem.

Snyder linked arms with his players on the sideline, flanked by cornerbacks Bashaud Breeland and Josh Norman, while wide receivers Jamison Crowder and Brian Quick, tight end Jordan Reed and linebackers Ryan Anderson and Chris Carter took a knee.

Seconds before kickoff, Redskins officials released a two-paragraph statement that made no reference to Trump or the presidency but extolled football as “the great unifier” and stated that the team would “work to address divisions and bring unity, civility and respect” to the community.

What makes Sunday’s mass demonstrations by NFL players particularly notable is that the league demands conformity far more than other pro sports leagues, devoting lengthy sections of its rulebook to the height of players’ socks, for example. Players are most prized for executing assignments precisely as directed, and because NFL careers are short and contracts aren’t guaranteed — unlike those of NBA or Major League Baseball players — outspoken players who create distractions often do so at their peril.

NFL Commissioner Roger Goodell and DeMaurice Smith, the NFL Players Association’s executive director, spoke Saturday about Trump’s comments but didn’t coordinate a response, according to one person close to the situation. Sunday’s on-field displays, rather, reflected individual teams’ decisions rather than an orchestrated leaguewide effort.

The Ravens-Jaguars response reflected that: players and coaches choosing whether to stand or kneel yet linking arms in solidarity. Khan, the Jaguars’ owner, explained afterward that he considered it a privilege to stand with his players and show unity and support for diversity of race, faith and opinion in the face of the president’s “divisive and contentious” comments.

Mark Maske in Philadelphia, and Cindy Boren and Brian Murphy contributed to this report.