Just reading through J.R.R.Tolkien: A biography by Humphrey Carpenter again and I found this quote that might be helpful.
It's found on page 89.
"Discussing one of the principal characters in The Lord of the Rings he wrote many years later: ' My "Sam Gamgee" is indeed a reflexion of the English soldier, of the privates and batmen I knew in the 1914 war, and recognised as so far superior to myself."