At Survivor Series on November 22, 2015, Sheamus won the WWE World Heavyweight Championship after cashing in his Money in the Bank contract on Roman Reigns. Sheamus then defended the title in a rematch on the November 30 episode of Raw, but the match was interrupted by Alberto Del Rio (the then-United States Champion), King Barrett and Rusev. Sheamus subsequently announced that the four wrestlers, all born outside the United States, had formed "The League of Nations". The group had their first match together later that night, teaming with then-WWE Tag Team Champions The New Day (Big E, Kofi Kingston and Xavier Woods) to defeat Reigns, Dean Ambrose and The Usos in a 7-on-4 handicap match. On the December 3 episode of SmackDown, the entire League of Nations lost to Roman Reigns via count-out in the 4-on-1 handicap main event match. The League of Nations were then involved in a 16-man fatal four-way elimination tag team match on the following episode of Raw, facing The Wyatt Family (Bray Wyatt, Braun Strowman, Luke Harper and Erick Rowan), The ECW Originals (The Dudley Boyz, Tommy Dreamer and Rhyno) and the team of Reigns, Ambrose and The Usos; the match culminated in Reigns pinning Sheamus.
While maintaining a group rivalry with Reigns and his allies, members of The League of Nations also had individual storylines, as Jack Swagger started a feud over Del Rio's United States Championship, while Rusev was written into a story with Ryback. Both of these angles culminated at TLC: Tables, Ladders & Chairs, where all of the League members were successful in their separate singles matches, with Del Rio and Sheamus both retaining their championships (the latter needing help from his cohorts). However, Sheamus' WWE World Heavyweight Championship run ended the following night on Raw when he lost the title back to Reigns, ending his reign at twenty-two days. He had a rematch against Reigns on the January 4, 2016 episode of Raw, but failed to regain the title even with Mr. McMahon acting as the special guest referee. On the January 11, 2016 episode of Raw, Del Rio lost the United States Championship to Kalisto, only to regain it the following day at the tapings for SmackDown after interference by Barrett. At the Royal Rumble event, Del Rio once again lost the championship to Kalisto. He, Rusev, and Sheamus participated in the Royal Rumble match, but were all eliminated by Reigns.
Del Rio received a United States Championship rematch, which was contested in a two-out-of-three-falls match, on February 21 at Fastlane, which was unsuccessful. Also at Fastlane, The League of Nations entered into a feud with then-Tag Team Champions The New Day, who had become fan favorites since they had been paired together in December. They mocked The League of Nations in skits by calling them the "league of booty". Sheamus and Barrett unsuccessfully challenged Big E and Kingston for their titles at Roadblock on March 12, and Del Rio and Rusev were defeated by Big E and Woods in another title bout the following night on Raw, prompting all four members to attack The New Day after the match. The League of Nations then challenged The New Day to a match at WrestleMania 32 on April 3, where they defeated The New Day, but were attacked by Mick Foley, Stone Cold Steve Austin and Shawn Michaels after the match.
On the April 4 episode of Raw, Barrett and Sheamus faced The New Day in another tag team title match, in a losing effort. After the match, the other League of Nations blamed Barrett for being the "weak link" and attacked him, ejecting him from the group, before the rest of the team was attacked by The Wyatt Family. This marked Barrett's last appearance for WWE before his release from the company in May. The storyline with The Wyatt Family was cut short later that month after Bray Wyatt legitimately suffered an injury to his right calf. In their final appearance together, the group competed in a six-man tag match against Cesaro, Kalisto, and Sami Zayn on the April 28 episode of SmackDown, but Del Rio and Rusev walked out during the match and Sheamus, who did the same, confronted Del Rio and Rusev during a brawl, and disbanded The League of Nations.