The Red Sox were a dominant team in the new league, defeating the Pittsburgh Pirates in the first World Series in 1903 and winning four more championships by 1918. However, they then went into one of the longest championship droughts in baseball history, dubbed the "Curse of the Bambino" after its alleged inception due to the Red Sox' sale of Babe Ruth to the rival New York Yankees two years after their world championship in 1918, an 86-year wait before the team's sixth World Championship in . The team's history during that period was punctuated with some of the most memorable moments in World Series history, including Enos Slaughter's "mad dash" in , the "Impossible Dream" of , Carlton Fisk's home run in , and Bill Buckner's error in . Following their victory in the 2018 World Series, they became the first team to win four World Series trophies in the 21st century, with championships in , , and . The team's history has also been marked by the team's intense rivalry with the New York Yankees, arguably the fiercest and most historic in North American professional sports.