Sunday football fans were greeted to empty sidelines, kneeling players and arm-locked teams as a show of unity or defiance, depending on their view of the now year-long anthem protests seen throughout the NFL.

How it got started?

Former 49ers backup quarterback Colin Kaepernick originally started the protest in the 2016 season by kneeling while The Star Spangled Banner before preseason games. He continued this during regular season, leading to much controversy. Kaepernick stated many times that his reasons for kneeling was to bring attention to police brutality against African-Americans.

Titans' Rishard Matthews changes tone on Colin Kaepernick

Who is involved?

Following Kaepernick's initial kneeling, the Seattle Seahawks stood linked arm and arm while four members of the Miami Dolphins took a knee, becoming the first NFL players outside of Kaepernick to join this protest. The protests have spread from there. Multiple players have joined in; including Seahawks' Michael Bennett, 49ers' Antoine Bethea and Eli Harold, Kenny Britt and Robert Quinn on the Rams, and many others have either joined in the protests or have come out in support of Kaepernick.

Related:Titans' Delanie Walker: 'No one's telling you to come to the game'

What’s the history of anthem protests?

Kaepernick is not the first do this type of protesting in sports. Former NBA guard Mahmoud Abdul-Rauf elected to not stand during the nation anthem during his breakout 1995-96 season with the Denver Nuggets citing his Muslim faith and his view of the American flag as a symbol of oppression and racism. “You can’t be for God and for oppression. It’s clear in the Quran, Islam is the only way,” Abdul-Rauf told reporters.

He was suspended for one-game and ended up having to compromise with the league to stand and pray with his head down during the anthem. Abdul-Rauf was traded to the Sacramento Kings and was not re-signed after his contract expired in 1998.

The most famous incident of anthem protest is the raised fists of Tommie Smith and John Carlos at the 1968 Olympics. Smith and Carlos’ protest was against social injustice, racism and discrimination during a time of high tension in the United States—six months after Martin Luther King Jr.’s assassination set off riots.

The two were suspended from the U.S. Olympic team.

What are the different sides of the issue?

Kaepernick’s goal was to bring attention to the many cases of police brutality against African-Americans, using both the high profile platform as an NFL player and the large stage provided by NFL games to raise awareness.

However, his, and those that have followed him, actions have been viewed by many as disrespectful to the military and as an unpatriotic move. All of the opposition to this move hinges around that argument.

Why the increase?

Sunday's mass increase of protests were in response to comments from President Donald Trump in an address at one of his campaign styled-rallied in Alabama and on his Twitter account that many in the NFL veiwed as an attack.

What did Trump say?

Trump's first wave of comments included the extremely decisive statement: "Get that son of a b---- off the field right now. Out. He's fired."

He continued with more comments on his Twitter account that double-downed on this idea.

Who all participated in Sunday's protests?

Several players from the Buffalo Bills, Denver Broncos, New York Giants, Detroit Lions, New England Patriots, New Orleans Saints and Atlanta Falcons did not stand for the anthem.

The Miami Dolphins, Tampa Bay Buccaneers, Minnesota Vikings, Philadelphia Eagles, Chicago Bears, Indianapolis Colts and New York Jets stood with arms locked, though some players from those teams chose to kneel. Members of the Dolphins also warmed up in "I'm with Kaep" shirts.

The Titans, Seahawks and the Steelers did not come out of the locker room for the anthem.

Who didn't?

The widespread protest did not included every player. Many players elected to stand for the anthem as normal. The most prominent of those is Steelers left tackle Alejandro Villanueva.

Steelers don't participate in national anthem, with exception of ex-Ranger Alejandro Villanueva

Villanueva is a former Army Ranger and West Point graduate who stood visible outside of the tunnel with his hand over his heart, while the rest of his team stood inside of the tunnel during the national anthem.

Not just a player protest

Players weren’t the only ones to participate in the protests on Sunday. Several owners linked arms with their teams, including Jacksonville Jaguars owner Shahid Khan, Philadelphia Eagles owner Jeffery Lurie and Washington Redskins owner Daniel Snyder.

Both of the anthem singers of the Titans-Seahawks and Falcons-Lions games took a knee following their performances. Rico LaVelle, the Falcons-Lions singer, took a knee and raised his fist before the line “And the home of the brave” in The Star Spangled Banner. Meghan Linsey took a knee after finishing her rendition at the Titans-Seahawks.

Related:Meghan Linsey gets death threats after taking a knee at Titans-Seahawks

What was the reaction?

Mixed to say the least.

Many came out in support, taking to Twitter using the hashtag #TakeAKnee to showcase their support for both the movement itself and the players right to protest. Some, like the group of 50 fans in Nashville decided to participate in their own anthem protest at the Titans-Seahawks game by sitting peacefully during the anthem. The group did stand for the presentation of the flag.

The other side of the issue also took to Twitter with their own hashtag #StandForOurAnthem, spearheaded by Trump, and calling for boycotts of NFL games.

More:Titans' Walker received death threats since comments about anthem

More on Trump and NFL

Titans, Seahawks protest: Teams stay in locker room for national anthem

Anthem singer: Meghan Linsey kneels after singing anthem

Rexrode: Titans and NFL players have spoken, and they also need to listen

NFL: No punishment for players who were not present on sideline for anthem

Tom Brady speaks: Says he disagrees with Trump's NFL comments

Trump unites: Rhetoric forces NFL teams to take stand as owners, players unite

More: NFL player protests sweep league after Donald Trump's hostile remarks

Reach Autumn Allison at aallison@gannett.com or follow her on Twitter: @Aallison_TN.