It will load the game world & mission progress of the host’s save. The progress of the joining player does not matter. When joining someone for the story mode, be aware that story-related trophies & achievements can only be unlocked by the host, not by the joining player (everything that says Solo Campaign Only in the description can be unlocked in co-op but only by the host). When the host initiates a Spec Ops mission, the friend that joined will get a popup in the top right corner of the screen to accept it. They are only available after finishing the prologue island “Isla Santuario” and having reached one of the 3 main camps. After your friend joined, the host can simply talk to the Spec Ops NPC at one of the main camps in Madrugada, Valle De Oro, El Este to start these missions. These are extra maps with different objectives, such as stealing batteries from enemy camps and extracting them from the mission area. There is also co-op for the online mode “Special Operations”. Co-Op Unlock Requirement: Co-Op is only available after finishing the Main Mission DU or Die on the prologue island “Isla Santuario”, which takes about 1-2 hours of playtime! Co-Op is not unlocked from the beginning.