Missions of the green berets,marines..etc?

What type of missions do the different forces do..for example: the green berets rescue people from?? hostage? the marines...etc....the army....and which type of force does missions such as the one ill describe: A small group of about 4,they have to survive in a jungle by gathering their own food..etc..and they cannot be spotted as they have a mission in that terrain....so which force(marines,army,navy..etc) does these types of missions? thankks =]