Ever since they announced the title I've been convinced "Ground Zeroes" refers to the birth of Solid and Liquid. This along with EVA, zero, etc. would be the center storyline of the Ground zeroes while Phantom Pain fast forwards 9 years to find a young solid snake sent on a sneaking mission by the very system that big boss is out to destroy. Poor solid snake was always just a pawn by the patriots while Big Boss, Solidus and Liquid knew what the hell was going on.