Metal Gear Solid 4 is set in 2014, nine years after the plot of Metal Gear Solid and five years after Metal Gear Solid 2: Sons of Liberty. The world economy relies on continuous war, fought by PMCs, which outnumber government military forces. PMC soldiers are outfitted with nanomachines that enhance their abilities on the battlefield. The control network created through these nanomachines is called Sons of the Patriots (SOP), and Liquid Ocelot is preparing to hijack the system. Snake, meanwhile, is experiencing accelerated aging due to his status as a clone, and has less than a year to live. When his former commanding officer Roy Campbell approaches him with one last mission - to terminate Liquid - Snake accepts and is dropped into the Middle Eastern war zone where Liquid is believed to be hiding.