MGS: Portable Ops included Silo entrance, which became Silo Sunset, and locations in MGS4 spurred Midtown Maelstrom, Virtuous Vista and Icebound Inferno. Forest Firefight and Ravaged Riverfront are also loosely based on the forest area in MGS3 and the Eastern Europe area in MGS4.
The game "MGS: Portable Ops" included locations like Silo entrance which became Silo Sunset, and locations in "MGS4" inspired Midtown Maelstrom, Virtuous Vista, and Icebound Inferno. Forest Firefight and Ravaged Riverfront are also loosely based on the forest area from MGS3 and the Eastern Europe region of MGS4.