Call of Duty: Modern Warfare 2, released in 2009, uses an extensively modified version of the
IW engine, which is a game engine developed by Infinity Ward. The IW engine has been used for several games in the
Call of Duty franchise, with each new iteration typically featuring significant enhancements and improvements over the previous one.
It's important to note that while it's common for developers to use pre-existing engines as a base (like Unity or Unreal), many big studios prefer to use proprietary game engines tailored specifically to their needs. These engines are often optimized for the specific type of game they're developing, allowing the team to maximize the performance and visual fidelity of their games. In the case of
Modern Warfare 2, the IW engine was altered to improve the game's physics, visual effects, and level destructibility.