Michael Cole tries to gain insight on the motive for the recent actions of Dean Ambrose, Roman Reigns and Seth Rollins.

WWE is under attack … sort of.

Technically, “The Shield” — NXT standouts Dean Ambrose, Seth Rollins and Roman Reigns — don’t see themselves as renegades, invaders or mercenaries of any kind, and they’re not here to simply attack anyone. According to the three, they are simply purveyors and protectors of justice in a WWE that has long since lost its moral compass. Their goal is to right wrongs, not cause chaos. But chaos is what they’ve left in their two short weeks since storming into Survivor Series and powerbombing Ryback through a table.

While The Shield’s true motives and allegiance remains foggy at best, though, it’s tough to ignore the similarities between their forcible foray into the world of WWE from the outside. WWE has been subject to invasions, attacks and sieges from almost every vengeful outsider the WWE Universe can dream up, from rookies to rivals to everything in between. But WWE has also been on the other side of the fence as well, sending troops out into enemy territory to expand its own borders and lay claim to vulnerable corners of the sports-entertainment landscape.

In other words, it’s a tough world out there and only the strong survive. As The Shield continues its vicious incursion, WWE.com counts down some of the most memorable invasions in wrestling history, from the brutal to the bizarre to the downright extreme.

We think, given the circumstances, we’ll begin with an invasion that a group of NXT veterans can probably appreciate.

The Nexus

SmackDown: The Nexus invades the live debut of SmackDown on Syfy

The inaugural class of WWE NXT Rookies wanted to make an impression in their WWE debut, so they made it in the biggest way possible: They literally tore the house down. During a “Viewer’s Choice” episode of Raw, the nefarious newbies swarmed the ring during John Cena’s match against CM Punk. Clad in matching T-shirts, the Superstars perpetuated a brutal beatdown on Cena, Punk, Luke Gallows, color commentator Jerry Lawler and the particularly unfortunate ring announcer Justin Roberts before dismantling the ring, piece-by-piece. It turned out the act, now firmly lodged in WWE legend, was both a savage mission statement and a dark harbinger of things to come.

In the months that followed, the “Nexus” — under the stewardship of WWE NXT season one winner Wade Barrett — would follow up their symbolic disassembly of the ring with a literal decimation of the WWE roster. At Barrett’s behest, the black-and-yellow–clad goon squad operated under the sole principle of “If you’re not Nexus, you’re against us,” and those who were deemed “against us” were truly shown no quarter. While Barrett’s quest to claim the WWE Championship for himself didn’t quite pan out, The Nexus did strike championship gold when Heath Slater & Justin Gabriel claimed the WWE Tag Team Titles. Barrett achieved one towering victory when Cena was forced to assimilate into his ranks for a number of weeks, and another when he briefly fired Cena from WWE altogether after the Englishman found himself fed up with the Cenation leader’s refusal to commit to the cause.

For all of its bravado, however, The Nexus met a fairly ignominious end in 2011 after control of the team was wrested from Barrett by (ironically enough) CM Punk. While Barrett and fellow defectors Slater & Gabriel formed The Corre on SmackDown, The Second City Saint recruited a new class of rookies to fill out his flock (Husky Harris, Michael McGillicutty and Mason Ryan) and re-christened them as the “New Nexus.” But his efforts to reform the Nexus into his own personal cultish army fell short when his disciples were systematically eliminated by Randy Orton in the months leading up to WrestleMania XXVII, with the team quietly disbanding after Punk laid claim to the WWE Championship in July 2011.

The Invasion

William Shakespeare himself couldn’t have written the familial crisis that befell the McMahon family in spring 2001 when Shane McMahon purchased the folding WCW from under his father’s nose, robbing The Chairman of what should have been the crowning victory of the Monday Night War. While Shane assumed control of Eric Bischoff’s roster, Stephanie twisted the knife by buying ECW and hiring Paul Heyman as her General Manager. The two bickering siblings set their squabbles aside and joined forces in an all-out effort to topple the clan’s preening paterfamilias by initiating a monthslong saga that simply became known as “The Invasion.” Kick-started by WCW Champion Booker T, who attacked “Stone Cold” Steve Austin at King of the Ring ’01, the Invasion consisted of wave after wave of WCW and ECW wrestlers causing endless mayhem for the denizens of WWE. Things became so tumultuous for the McMahons that no less an icon than Austin himself defected from WWE, assuming the role of general for the villainous Alliance and breaking the collective hearts of the WWE Universe in the process.

The chaos boiled over into Survivor Series, where the McMahons agreed on a Traditional Survivor Series Elimination Tag Team Match between WWE and The Alliance. And to the victor, as they say, would go the spoils: The victorious team would assume control of all three companies. The historic bout was truly an all-out effort (Shane-O Mac even suited up for The Alliance’s side), but despite a dastardly betrayal by Chris Jericho, The Rock scored the final pinfall for WWE to seal Mr. McMahon’s empire and end Shane and Stephanie’s WCW/ECW Alliance for good.

The Outsiders

Scott Hall declares war on WCW.

Something wicked came to WCW in the ’90s when Scott Hall jumped ship from WWE, infiltrating Eric Bischoff’s roster as an interloper who was spoiling for a fight. “You know who I am,” Hall told the Monday Nitro crowd upon his arrival, “but you don’t know why I’m here.” Hall promised big surprises for the Nitro roster, and delivered the next week in the form of his accomplice, Kevin Nash. Throughout the next number of weeks, “The Outsiders” raised hell and caused ruckus where the big boys played, assaulting WCW competitors and leaving a general trail of devastation in their wake, all while teasing the presence of a mysterious third member who had yet to reveal himself.

Of course, we all know what happened next. The third man turned out not to be another new invader, as he’d been in WCW for a while by that point. But he was a defector, brother.

The final Outsider ended up being none other than Hulk Hogan, who cemented his allegiance to Hall & Nash by unleashing his world famous Leg Drop on a prone “Macho Man” Randy Savage at Bash at the Beach. While the WCW faithful pelted The Hulkster and his cohorts with garbage and unleashed waves of boos upon the traitors, Hogan brazenly damned the fans who’d supported him and declared the trio to be the “New World Order of wrestling” to a flabbergasted “Mean” Gene Okerlund. The nWo, in case you haven’t heard, went on to be a very big, very dangerous deal in the world of sports-entertainment. There’s even a home video out about them.

The DX invasion of WCW

DX tries to invade the back entrance of Nitro.

Now here’s an odd one: an invasion where one side never technically breached the other’s lines. During a stop in Virginia in April 1999, Raw and Nitro broadcast from arenas only a few miles apart from each other. The proximity between the two meant the situation was ripe for dirty play. Given that this was at the height of D-Generation X’s ascent through WWE as well as the apex of the Monday Night War, that meant there was really only one thing for Triple H & co. to do: They decided to pay the big boys a visit.

The King of Kings and his merry band of anarchists commandeered an army jeep and went on a one-team propaganda tour across Virginia, screaming insults through a bullhorn and sporting black “POWCW” (“Prisoner of WCW”) armbands across their wrists in an attempt to forcibly infringe on enemy territory. Though DX made it to the doorstep of WCW’s host arena, the crew was unfortunately barred at the last minute by building security and forced to turn back.

WWE invades ECW

As anyone who saw One Night Stand 2006 can attest, Jerry “The King” Lawler does not like ECW. But what the WWE Universe may not know is the WWE Hall of Famer’s distaste for the Extreme Philadelphia promotion goes all the way back to the ’90s, when Lawler and a small WWE contingent took the budding rivalry to the boiling point by crossing enemy lines.

In a crass, unthinkable act of aggression, Lawler and Jim Cornette besieged the ECW Arena, laying waste to ECW’s finest in an unwarranted, unpredictable display of ferocity from the Philly crew’s big-city rivals. “The King” also notched himself a marquee moment in the invasion when he submitted Tommy Dreamer to one of the most painful-looking canings in history. In a merciless act of aggression, Lawler whacked The Innovator of Violence in the crotch with a Kendo stick, an atrocity so extreme that it sent Dreamer to the hospital. (Joey Styles still flinches when he tells us the story.)

The ECW faithful got some consolation, though. Lawler eventually lost a one-on-one contest to Dreamer at Hardcore Heaven and, following ECW’s resurrection in 2006, suffered a humiliating, immediate loss to Tazz (with an assist from Styles) in the bowels of the Hammerstein Ballroom in New York City.

We guess that’s the way invasions go: You win some, you lose some. Whether The Shield comes up on the winning side of things remain to be seen. That history is not yet written.