In a recent interview with VG247.com (linked above), it was revealed that the original build of Modern Warfare 2 had a co-op campaign mode.
Infinity Ward's Robert Bowling briefly commented about it along with detailing a "substitute" for the co-op mode, Spec Ops mode.
To quote from the interview: "We did it early on; that's what Spec Ops started out as, as co-op through story," said Bowling when asked why Campaign co-op didn't make the final game.
"But it really broke the cinematic experience, took the immersion out of it, out of the story and the pacing and everything we'd spent so long crafting.
It just ruined the experience we were aiming for, so we took it out, kept the single-player for that one player intact and polished it."
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