Why was Captain Price in prison in Modern Warfare 2?

In the concluding fight of Modern Warfare 1 (the one on the bridge), it is implied that Price is killed (he gets shot a few times). However, it turns out that he was only captured (although you don't see him being captured as you're too busy doing your thing).

Everything here is good guessing, and I believe Infinity Ward did not put "Operation Kingfish" until after 2012(actual life, not ingame). This link has the answer to why Price was in the Gulag. And Kamarov was an ally, not an enemy, because he opposed Makarov. That is why he helps you on the bridge, both of you are enemies to Makarov. Kamarov was actually a Loyalist.

http://callofduty.wikia.com/wiki/Operation_Kingfish

There is also a film based on the mission. The link for the video is also in the top link.

It also says not to respond to other people's answers, but I noticed somethings were a bit ...wrong. There were different types of Russians, hard to explain, but if you read this http://callofduty.wikia.com/wiki/Ultranationalists it might make some more sense when you play.