The Shellshock series are Third-person Shooter and a First-person Shooter games, developed by Guerrilla Games and Rebellion Developments and published by Eidios Interactive, first making its debut in 2004 with Shellshock: Nam '67 on PC (Microsoft Windows), Xbox, and PlayStation 2, and then in 2009 with Shellshock 2: Blood Trails on PlayStation 3, Xbox 360, and PC (Microsoft Windows).
Shellshock: Nam '67 is a Third-person Shooter game, based in the Vietnam War in 1967. The player takes control of Pvt. Caleb "Cal" Walker, who is newly drafted into the U.S. Military. He fights through the war alongside other G.I.'s and the South Vietnamese Army against the North Vietnamese Army and the Viet Cong. Shellshock: Nam '67 is developed by Guerrilla Games.
Shellshock 2: Blood Trails is a First-person Shooter game, taking place two years after the events of its prequel. This time, the player takes control of Pvt. Nathaniel "Nate" Walker, a newly drafted G.I. who was brought to his brother Cal for questioning on the Whiteknight virus, whom he had been infected with, only to follow him around Vietnam throughout the war and fighting off other victims of the virus, as well as the Viet Cong forces. Shellshock 2: Blood Trails is developed by Rebellion Developments.
While the first game is based off of the typical events of war, during the Vietnam War, the second game takes aspects from both realistic and fictious events. The first game is action-based, while the second is horror-based. The gameplay and mechanics between the two games are very different from each other, taking separate skill sets to play. Both stories however, remain in the same timeline.