"The White Company", & "Sir Nigel" by Sir Arthur Conan Doyle (14th Century/Hundred Years War... & apparently what Conan Doyle would have liked to have been remembered for writing, rather than the Sherlock Holmes stuff)

"Death To The French by C.S. Forester (Napoleonic - Peninsular War)

& Sci-Fi, the "Hospital Station" Series by James White (think I got the name right)