It’s hard to believe how much things change in a decade. While the battles inside WWE rings are going strong, there hasn’t been an outside threat to the organization as a whole since 2001, when the stars of  WCW and  ECW united to try and take down WWE.

Mr. McMahon’s own children,  Shane and Stephanie, tried to take down their father’s sports-entertainment empire, selling their shares to buy his competition. WCW and ECW’s Invasion started an all-out war the likes of which had never been seen before.

See the Invasion in photos

From the first strike to the final battle, The Invasion was one of the most unpredictable periods in WWE history. Relive years of pent up tension unleashed in sports-entertainment’s biggest conflict.

March 26, 2001: A McMahon buys WCW

For months, rumors had been swirling that WCW was up for sale. After Monday Nitro led the Monday Night War, defeating Raw for 82 straight weeks in the Nielsen ratings, the Atlanta-based promotion had been on a steady decline, burning through tens of millions of dollars. Finally, parent company AOLTime Warner, tired of bleeding money, put word out that WCW was available.

It seemed as though former WCW President Eric Bischoff had put together the winning bid with Classic Sports Network founder Brian Bedol (who then sold the network to ESPN) and would re-assume control of the company until March 2001. AOL Time Warner executive Jamie Kellner no longer wanted wrestling on TNT and TBS, leading Bischoff and Bedol to withdraw their offer. WWE Chairman Mr. McMahon swooped in at the last moment on March 23, purchasing all of WCW’s assests, or so he thought.

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The Chairman gloated throughout the entire March 26, 2001 episode of Raw in Cleveland, part of which was being simulcast on WCW’s flagship program. Mr. McMahon was taking delight in picking and choosing what WCW talent he’d be hiring or firing. Basking in the glory of defeating his biggest competition, he planned on signing the paperwork to make the sale final in the ring at WrestleMania X-Seven.

There was plenty of reason to celebrate until the music of his son and WrestleMania opponent, Shane McMahon, blared through the arena. Mr. McMahon put up his dukes, ready for a brawl, until he realized that The Boy Wonder wasn’t at Raw. Shane was almost 1,000 miles away, in Panama City Beach, Fla., entering the WCW ring on the final episode of Nitro.

He informed his father that his ego had gotten the best of him once again. “The deal has been finalized,” Shane said. “The name on the contract does say ‘McMahon.’ However, the contract reads ‘Shane McMahon!’” The WWE Chairman was frozen in shock in the middle of the ring as his son informed him that he intended on bringing WCW back to its former glory and steamrolling over WWE in the process. The battle lines had been drawn.

Watch Shane McMahon's blockbuster announcement

May 28, 2001: WCW strikes first

Shane McMahon defeated his father at WrestleMania X-Seven in a vicious Street Fight, but remained fairly silent afterwards. Nothing was heard from McMahon or  WCW for nearly a month. Little did WWE know that the younger McMahon was laying in wait, preparing for his first strike against his father and WWE.

The opening attack of The Invasion came on May 28, 2001. Steve Blackman and  Perry Saturn were in the midst of a hard-hitting brawl on Monday Night Raw, when WCW star  Lance Storm rushed into the ring. The former  United States Champion floored Saturn with a superkick and was gone quicker than a bolt of lightning. Storm, having shocked the WWE Universe, raced out of the arena and met up with an elated Shane McMahon. The battle lines had been drawn, but WCW’s attack was just beginning.

For weeks, WCW competitors jumped WWE Superstars from behind, making it known that the revived company was no joke. The opening barrage reached its apex at the 2001 edition of King of the Ring, when WCW Champion Booker T appeared out of nowhere and sent WWE Champion “Stone Cold” Steve Austin crashing through a table.

The next night, the war continued on WWE’s home turf: Madison Square Garden. WCW embarrassed Mr. McMahon once again as Mike Awesome took advantage of the 24/7 Rule on the WWE Hardcore Title, defeating a dazed Rhyno in the bowels of The World’s Most Famous Arena.

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WCW had WWE right where it wanted just a few weeks into the interpromotional battle. However, a wrinkle would be thrown into the war that would make it a little more … extreme.

July 9, 2001: An Alliance is formed

WCW wasn’t the only sports-entertainment company to meet its demise in 2001. There was another organization that saw itself as the leaders of a revolution in the industry, making things a little more in-your-face, a little more hardcore.  ECW had a passionate, dedicated fan base hungry for extreme action and ready to follow the company to the ends of the earth. And if there was going to be a war for supremacy, then they were going to force themselves right into the middle of it.

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On the July 9 edition of Raw, WCW’s Lance Storm and Mike Awesome took on WWE’s  Kane and Chris Jericho. Kane and Y2J had the upper hand on the invaders in their former home base of Atlanta. The Big Red Monster had Awesome in his clutches, about to chokeslam him, while Jericho had Storm trapped in the Walls of Jericho. However, chaos broke out when the Extreme Original, Tommy Dreamer and Rob Van Dam, formerly of ECW, jumped the guardrails and attacked Kane and Jericho. The WWE Universe watched on in shock as Awesome and Storm sided with the rebels, joining in on the beat down.

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Things took an even stranger turn when WWE troops rushed to the ring in what looked like a rescue mission. The Dudley Boyz, Raven, Rhyno, Justin Credible and Tazz, all WWE Superstars, stared down the four invaders for a few moments. Then, they ominously turned toward Kane and Jericho.

“Feel it, JR,” Raw commentator and former ECW owner  Paul Heyman screamed at his partner. “Feel this moment for the rest of your life!”

Like clockwork, as soon as Heyman finished talking, the eight Extremists  jumped the WWE Superstars, viciously attacking them with fists, boots and steel chairs. It was official, ECW had joined the Invasion.

Shane McMahon approached his father about uniting to take out ECW later that night. The WWE/WCW union was short-lived, as the two warring sides couldn’t co-exist in the Raw main event. The rivalry was taken to new heights when the WCW and ECW factions embraced in the ring as a confused Mr. McMahon watched on.

The WWE Chairman stood in shock as his son explained that he may not be able to compete with WWE’s checkbooks, but he can outsmart his old man. Shane announced that WCW and ECW had merged at the behest of him and the new owner of ECW, his sister Stephanie!

Watch: The Alliance is born

With the McMahon family splintered between the three companies, it seemed as though WWE was crumbling. However, there was still one major blow left to be dealt to Mr. McMahon.

July 22, 2001: Benedict Austin

The war was supposed to come to a head at the Invasion pay-per-view. A series of ten matches pitted WWE’s top Superstars against the best WCW and ECW, now known as The Alliance, had to offer. WWE Tag Team Champions  John “Bradshaw” Layfield and  Ron “Faarooq” Simmons handily defeated WCW titleholders Sean O’Haire and Chuck Palumbo. WCW Cruiserweight Champion  Kidman was victorious over WWE Light Heavyweight Champion X-Pac in a mid-air collision of high-flyers. Even the referees got in on the action as WWE official Earl Hebner vanquished WCW’s top referee, Nick Patrick.

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However, it was the evening’s main event that drew the most attention. With the score tied 5-5, this would theoretically decide who won the war. Dubbed the “Inaugural Brawl,” The Alliance fielded it’s top five combatants (Booker T, Diamond Dallas Page, The Dudley Boyz and Rhyno) against WWE’s best ( “Stone Cold” Steve Austin, The Undertaker, Kane, Chris Jericho and Kurt Angle).

Pandemonium broke out quickly in the match. No official could keep tabs on all the warriors brawling around ringside. In the middle of the fracas, Shane McMahon knocked his father out with the WWE Title. Kurt Angle looked to have the battle wrapped up for WWE, with Booker T secured in the Ankle Lock, when one of the most shocking events in WWE history took place.

FULL MATCH: Watch the Inaugural Brawl in its entirety

Austin, then the WWE Champion, booted Angle in the face before hitting him with the Stone Cold Stunner. The Texas Rattlesnake put Booker on the prone gold medalist for the pin, giving The Alliance the win. Anything that could have gone wrong for WWE in this war for survival did. Was there any way they could recover from the crippling defection of the WWE Champion?

July 26, 2001: The tides turn

With Steve Austin now The Alliance’s centerpiece, Mr. McMahon and WWE had their backs against the wall as they searched for a new Superstar to rally the troops around. Luckily, the search didn’t take long.

The Rock had not been seen since losing to Austin at WrestleMania X-Seven. As summer’s end drew near, however, Shane McMahon let The Great One know he’d be more than welcome to join The Alliance upon his return. He wouldn’t have to wait long to get an answer. On the July 30 edition of Raw, Mr. McMahon and his son joined the returning Rock in the ring, begging him to join their factions.

The Great One seemed to make up his mind, taking out The WWE Chairman with a devastating Rock Bottom. Shane danced around the ring with glee, thinking he had pulled off the biggest coup of the year. The Boy Wonder was put in his place when he, too, was the victim of a Rock Bottom. The unusually quiet People’s Champion broke his silence, revealing that his motivation wasn’t McMahons, but the people.

“Finally, The Rock has come back … to WWE!”

The Alliance finally showed a sign of weakness around this time, too. In the middle of a WCW World Title Match between  Booker T and Kurt Angle on SmackDown, “Stone Cold” Steve Austin tried to help Booker keep the championship, laying out Angle with a Stone Cold Stunner. Booker, after getting back to his feet via Spinaroonie, seemingly had the match won, when Angle tripped him up and applied the Ankle Lock, forcing the tap out. The gold medalist had embarrassed The Alliance and Austin, bringing the WCW Word Title to WWE.

Angle’s reign didn’t last long, as Booker regained the championship days later. However, The Rock stepped into challenge Booker T for the WCW World Title at SummerSlam and defeated the Champion to bring the enemy’s title to WWE once again.

FULL MATCH: Booker T and The Rock battle for the WCW Title at SummerSlam 2001

With Kurt Angle and The Rock stepping up to lead the way, WWE had a newfound confidence as the war drew to a close. The final battle was approaching. Who would come out on top?

Nov. 18, 2001: Winner Take All

As Thanksgiving approached, the battle for sports-entertainment supremacy reached a fever pitch. Mayhem ruled WWE as more Superstars defected to The Alliance. No defection stung more than Kurt Angle’s. The gold medalist shocked the WWE Universe, unleashing a brutal chair attack on his former fellow WWE Superstars.

It was clear that the war had to end. It was agreed on that  Survivor Series 2001 would be the final battle. The main event would be a ten-man, Winner-Take-All Survivor Series Elimination Match. At the end of the night, only one company would be left. Mr. McMahon planted seeds of distrust among The Alliance beforehand, guaranteeing that one of their own would stab them in the back at the pay-per-view, hinting that it might be The Texas Rattlesnake.

Shane McMahon captained his own team, joining forces with Angle, Austin, Rob Van Dam and Booker T. They faced a WWE team of The Rock, Chris Jericho, The Undertaker, Kane and Big Show. The final battle was thrilling, with bodies and weapons flying everywhere.

Watch the final battle between WWE and The Alliance

Amid the carnage, Austin and The Rock were the final two Superstars in the ring. The rekindling of their WrestleMania rivalry held the fate of both WWE and The Alliance of WCW and ECW . In addition, the WWE Universe was waiting to see if Austin would indeed re-join the WWE ranks. However, it turned out Mr. McMahon was playing mind games with his enemies, as Kurt Angle rushed into the ring and clocked Austin with the WWE Title, revealing he had been the mole inside the Alliance!

Watch Angle's shocking revelation

Angle’s recon mission gave The Rock the opportunity to plant Austin with a Rock Bottom and win the match for WWE, eliminating The Alliance once and for all.

WWE had weathered the strongest challenge it had ever faced. With The Alliance gone once and for all, the Superstars were ready to take on any and all challenges that lied ahead.