It "took years" of development to rebuild the Assassin's Creed engine for the online co-op gameplay that's featured in Assassin's Creed Unity, according to senior producer Vincent Pontbriand.
Fans have called for the ability to play AC games co-operatively for some time, yet the series has only just received the feature in its seventh iteration.
In a recent interview with CVG, Pontbriand explained why the studio has taken this long to implement the feature.
"Because it's very complicated to do," he said. "Assassin's Creed was always a single-player game to begin with. It took us three games to introduce PvP (player versus player) [into Assassin's Creed Brotherhood]."
In that game, multiplayer was consigned to a separate mode, which was built for that purpose, while the single-player campaign remained on the original tech designed for solo gameplay. But in AC Unity, the campaign itself allows for co-op, which required significant reworking of Ubisoft's tech, explained Pontbriand.
"[AC Brotherhood's multiplayer] was in the same universe, but you were playing as a Templar avatar in a very separate game mode. In Unity, we set out to unify all these game modes into a single experience. That's when we decided that co-op should be the next main focus, but in order to do that we had to rebuild all of our systems to allow them to be replicated over a network and working online.
"It took years of development to reproduce and redraft all of our sandbox features for a shared online experience."
Ubisoft recently confirmed that it has turned its multiplayer focus to co-op for Assassin's Creed Unity, which means it will not include a competitive multiplayer mode.
The Assassin's Creed Unity release date is set for October 28 on PC, PS4, and Xbox One.