Avengers: Infinity War was the culmination of the past ten years of the Marvel Cinematic Universe. Every film in the franchise, to some degree, paved the way for all of the galaxy's mightiest heroes to come together to take on the Mad Titan as he attempted to collect all six Infinity Stones and decimate the universe. As the Russos have put it, it acted as the beginning of the final chapter of the book that started in 2008's Iron Man.