I recently rewatched Saving Private Ryan and was wondering, how was the training different between the types/units of infantry in the American military in WW2? For example, how would a regular private of been trained in the 101st airborne vs Rangers vs 1st Division?
This may not fully answer your question, but may be of interest to you. There is a 4-part documentary on Netflix titled "Behind Enemy Lines". It tells the story of the formation during WW2 of special units such as the SAS, Commandos, Paratroopers, etc. --and the specific reasons why those groups were formed.
It has some great candid interviews with some of the first members, and details the type of training they were given.