For most of Peace Walker's development, and even in early US promotional material, this 2010 PSP title had a grander designation - Metal Gear Solid 5: Peace Walker. The absence of a number on the final product can be put down to a hundred things: simple rejection of a 'main' entry being a portable title; the PSP itself entering its final years; perhaps a concern that series fans would revolt at the radical departure from Metal Gear Solid 4. Whatever it was, that number's existence says one thing about Kojima Productions' mindset with Peace Walker. This is no spin-off.
Rich Stanton's been working his way through the Metal Gear Solid games in a series of thorough retrospectives. Here's the rest of the articles:
It was, however, the culmination of several spin-offs - the Metal Gear Acids and Portable Ops - that had given Kojima Productions great expertise with the PSP hardware. Those games were good, but hadn't hit the heights of the mainline series. "The concept itself was created probably right after we released Metal Gear Solid: Portable Ops," Hideo Kojima told Eurogamer. "I thought I would pass it on to the younger staff in Kojima Productions." In a central theme of Metal Gear Solid's development history, Kojima instead ended up directing, producing and writing Peace Walker.
