Here's our sixth installment of the USA TODAY/Bloody Elbow Top 50 MMA fights in modern history.

Beau Dure has written up the next block at USAT's Fighting Stances blog. To start, here's our criteria:

Some of the 50 fights we'll list aren't necessarily the best MMA bouts, but all of them are milestones for one reason or another, for better or for worse. The idea is to show how the sport has evolved. These are the fights that made the sport what it is today.

Here's the next 5 fights:

• Randy Couture def. Chuck Liddell, June 6, 2003; UFC 43
  Although this fight was only for the UFC's interim light heavyweight title, it did as much to determine the future of the promotion and its marquee division as any fight. Since champion Tito Ortiz wouldn't fight Chuck Liddell, they brought in the aging Randy Couture to face Chuck for the interim title. Couture had been run out of the heavyweight division and few expected him to win. But Couture shocked the world, not for the first time and not for the last. Couture would go on to beat Tito Ortiz at UFC 44 and clear up any doubt about who was the best light heavyweight in the promotion.
  
• Quinton Jackson def. Chuck Liddell, Nov. 9, 2003; PRIDE: Final Conflict
  Only a few months later, Dana White sent Chuck Liddell to Japan to enter PRIDE's Middleweight (205lbs) Grand Prix. The plan was for Liddell to sweep through the tournament and face PRIDE champion Wanderlei Silva in the finals. Of course any plan that hinges on predicting the outcome of a sixteen man MMA tournament at the highest levels of the sport has some obvious flaws. In this case the flaw was Quinton "Rampage" Jackson who, as we've seen since, is just a really tough matchup for Liddell. Jackson took Liddell down and battered him on the ground, sending him home and cementing PRIDE's reputation as the premier MMA promotion in the world. The awesome depth of the 2003 PRIDE MW GP is still a who's who of the best of the division, and several fighters that are the best of all time.
  
• B.J. Penn def. Matt Hughes, Jan. 31, 2004; UFC 46
  B.J. Penn may not have been able to win the UFC lightweight belt in two attempts, but at UFC 46 against all odds, he was able to take the welterweight belt from Matt  Hughes. Although B.J. promptly walked away from the promotion for two years and abandoned the belt, his dominating victory over Hughes gave fans a reason to believe in "The Prodigy" again. Five years on its easy to forget just how dominating Hughes was at the time, but make no mistake, Hughes was at his absolute peak and B.J. beat him soundly winning the first of his two UFC titles a record he shares with Randy Couture.
  
• Chuck Liddell def. Tito Ortiz, April 2, 2004; UFC 47
  The UFC may not have had as deep a 205lb roster as their rival PRIDE in the middle of the decade, but that meant that the top UFC light heavies all got to fight each other (with the exception of "Babalu" Sobral). We got to see Chuck vs Randy (3x), Chuck vs Tito (2x), Chuck vs Vitor Belfort, Randy vs Tito, Randy vs Vitor(3x), and Tito vs Vitor. This fight was part of that series, a four-sided rivalry that drove the UFC in the crucial building period between UFC 40's initial breakthrough and the big breakthroughs of 2005. Don't underestimate the role of UFC 40-47 in breaking the promotion through to the new audience that watched TUF in 2005. The DVDs were in every Blockbuster in the country and many's the frat house that followed up a TUF episode with a batch of newly rented UFCs. This fight finally saw Chuck get Tito locked in the Octagon after almost four years of avoiding the fight. Tito was game, but the Iceman just seemed to have his number.
  
• Forrest Griffin def. Stephan Bonnar, April 9, 2005; The Ultimate Fighter finale
  Do I really have to explain why this fight matters? It has become a corner-stone of the UFC legend, the epic barn-burner of a fight that drew more tends of thousands of new viewers every minute it lasted. In the season finale of the pretty successful TUF debut season, Griffin and Bonnar dug deep and produced the kind of sloppy, no defense brawl that pretty much everyone loves. It wasn't exactly a technical display, but it packed the kind of real life drama into 15 heart-stopping minutes that you can only get from live MMA. America was watching and America was now hooked on the UFC.
  

Read Parts One, Two, Three, Four, Five and the Prequel.