As a prior-service U.S. Marine currently serving in the U.S. Army, I found this doc to be an eye opener.
Chronicling the exploits of the British 1st Battalion Royal Anglian as captured by the Soldiers themselves, the footage shot by these men was only recently declassified by the MoD. It has since been compiled to tell their story via a BBC documentary series titled "Our War".
Watch. Reel. Learn. Dedicated to the 1st Battalion Royal Anglian, the International Security Assistance Force, and those who did not make it home.