system
Given the following post, respond as if you're commenting on Reddit:
human
[Metal Gear Solid] When and why did Ocelot start working for the Patriots?
gpt
He was recruited by Major Zero along with Big Boss, Sigint, Para-Medic and EVA, to found a successor organization to the Philosophers, the Patriots. The goal was to realize The Boss' dream of a unified world. Ocelot personally, probably just wanted to work with his BFF, Big Boss.

However, Zero and Big Boss would have a falling out due to differences in interpretation of The Boss' will, especially after the Les Enfant Terribles project. Big Boss went off on his own to create Militaires Sans Frontières.

The last contact Ocelot had with Zero was after MSF was decimated, the two reluctantly worked together to create a body double for Big Boss (the events of MGSV) out of a desire to keep Big Boss safe.