The latest installment in the NHL's "Because it's the Cup" ad campaign pays homage to one of hockey's most cherished traditions: the handshake line.

It's something all sports fans can appreciate and hockey fans love. After weeks of violent play and increasing animosity comes one of the sports world's great shows of sportsmanship and respect. Players line up to shake hands, putting the pride and integrity of the game and of their franchise above their own.

The result is pretty powerful:

It's not just a moment sentimentalized by ad men or fans.

Bruins forward Brad Marchand, whose first trip to the postseason two years ago saw him on the winning side of four handshake lines and whose second trip saw him on the losing side after a first-round disappointment, summed it up during last year's playoffs.

"As much as you hate them when you’re playing against them, at the end of the day we’re all out there trying to do a job and play the game we love," he said. "To show each other that respect at the end and realize that everything that’s happened is just because we both want to win—it’s definitely a great tradition."

No one knows exactly when the tradition was born, according to the hockey Hall of Fame (via Sports Illustrated), but it has produced innumerable memories, whether coming from the winners, the losers or the players who just couldn't let go of the lingering anger of the series.

Jubilation of Victory

Being on the winning side of a handshake line isn't something that is easily described; a player has to experience it for himself to fully understand the moment and the emotions that are a part of it.

One of the most poignant recent examples came from a player for whom it seemed the moment might never come. Phoenix Coyotes captain Shane Doan, a 17-year veteran, had never won a series until his team beat the Chicago Blackhawks in six games last season.

Per the NHL and Helene Elliott of the Los Angeles Times:

If Doan's words—"nice to be on the other end"—seem like an understatement, there's good reason. The handshake line isn't about showboating in front of the opponent. In the face of one of pro sports' great accomplishments, it's about showing respect for the losing side.

This was evident when the Blackhawks and Detroit Red Wings shook hands at the end of their heart-pounding seven-game second-round series this season:

With the Red Wings moving to the Eastern Conference as part of the NHL's realignment plan for the 2013-14 season, there might not be another handshake line between these teams for a while, and there was no better way for the most recent chapter in one of the game's greatest rivalries to end than with a handshake, where players and fans of both franchises could step back and appreciate the rivalry and all the memorable moments it provided.

Agony of Defeat

The handshake line does not begin immediately after the series ends. The winning team is allowed to celebrate for a few minutes before the teams get together.

For the losing players, this wait must feel like an eternity.

These guys are in a 24/7 hockey mode for weeks, and sometimes months, chasing a common goal of winning the Stanley Cup. After all the physical play, dirty hits, heartbreaking losses and physical and mental exhaustion, you can tell from the looks on their faces that they cannot get off the ice fast enough.

Yet very few players skip the handshake line, because while you don't have to like the opposing team, there needs to be a respect among players.

"You hate your opponent so much more than you did at the start of the series," Marchand explained. "Things that happen out there obviously you don’t like and you want to kill the other guy for it, but that’s how it is. We do it, they do it, and at the end of the day we all know that we’re playing the game to win and it’s nothing personal."

When the Tradition is Broken

Sometimes, though, the frustration is just too much for players to handle, especially in a series that included a dirty hit or a play that crossed the line from a physical standpoint.

One former NHLer with an interesting take on the handshake tradition is former Bruins goaltender Gerry Cheevers, who enjoyed a 418-game career spanning two decades. In 2009, Cheevers shared his thoughts on post-series handshake lines with the Toronto Sun:

Gerry Cheevers thought the NHL's post-series handshake ritual was meaningless when he won two Stanley Cups during the 1970s.

"Do you really mean it?" Cheevers said of the tradition. "Do you say: 'Thanks for bashing my brains in the past seven games and taking $15,000 out of my pocket?' "

It's indeed difficult to imagine that players in these handshake lines are being honest when they say things like "good game" and "good series" to the players they just engaged in physical battles over the course of an intense series. The hate built up between the players combined with the anger of losing often creates some friction in these handshake lines.

One instance occurred during the 1996 Western Conference playoffs. Colorado Avalanche forward Claude Lemieux injured Red Wings forward Kris Draper with a dangerous hit along the boards (watch the hit here). Draper sustained a head injury and Lemieux was suspended two games for the hit.

After the series ended with the Avalanche winning in six games, Red Wings forward Dino Ciccarelli gave reporters a candid response when asked about his exchange with Lemieux in the handshake line, saying, "I can't believe I shook this guy's [freakin'] hand after the game. That pisses me right off."

A recent example of players arguing in a post-series handshake line came after last year's Western Conference Finals between the Los Angeles Kings and Phoenix Coyotes.

Shortly before Kings forward Dustin Penner ended the series with an overtime-winning goal in Game 5, his captain, Dustin Brown, made contact with Coyotes defenseman Michal Rozsival's knee at the blue line on an offside. The Coyotes, and Doan in particular, were not happy with the hit, and the two captains talked about the incident when they met in the handshake line (video below):

With the anger of defeat still on the minds of the players on the losing team, it's not surprising that we have seen a few awkward and heated exchanges between players at the end of a series.

Why It's Unique in Sports

The NHL is the only North American major pro sports league in which players and coaches make it a tradition to shake hands and show their respect for the opponents after every playoff series.

Also, unlike other sports, NHL players on opposing teams rarely shake hands or socialize on the playing field at the conclusion of regular-season or playoff games.

In the NBA, guys exchange fist bumps and hugs before heading to the locker room after games. LeBron James and Paul George actually high-fived in the middle of an Eastern Conference Finals game this year. In the NHL, one of the only times we see this kind of interaction is in the post-playoff series handshake line.

Even friends become enemies during NHL playoff series. Bruins forward Tyler Seguin recently explained to the Boston Herald how his friendship with Blackhawks star Patrick Kane, with whom he played in Switzerland during the lockout, will be impacted by the Stanley Cup Final:

Though Seguin considers Kane his bud, don’t expect the two to rehash their friendship until the series is over. 

“When it’s playoffs, you don’t know anybody out there except your teammates,” Seguin said. “It’s just kind of how it goes, especially the Stanley Cup finals. Both sides want it and both sides are going to work hard. Yeah, I guess you can call it a friendly relationship, but it’s also business.”

NHL players go into a super-competitive mode and don't come out of it until their team is done playing, even if one or more of the opponents are a personal friend.

That makes it all the more jarring when the intensity lifts.

One of the best examples was when Bruins goalie Tim Thomas and Tampa Bay Lightning forward Martin St. Louis, former teammates at the University of Vermont, met in the handshake line after the 2011 Eastern Conference Final.

"You know, I told him he's a warrior and that I love you, man," said Thomas when asked about his conversation with St. Louis in the handshake line. "He's just an incredible competitor. He puts everything he has into it and that's why it was so special to be his teammate."

It's a show of camaraderie that transcends competition.

Follow @NicholasGoss35

Nicholas Goss is an NHL Lead Writer at Bleacher Report. Nick was a credentialed reporter at the 2011 Stanley Cup Final and 2012 NHL playoffs, and he is also a credentialed writer at the 2013 NHL playoffs in Boston. All quotes obtained first hand or from the Bruins media website unless otherwise noted.