WW1
"All quiet on the western front" (the original 1920's version) is an excellent ww1 film- far superior to the 1970's version.
"Gallipoli" is good about the ANZAC (australian / newzeland) troops in the dardanelles in ww1
"Lawrence of Arabia" David Leans film of the story of T.E. Lawrence's campaign in the middle east.
"The Blue Max" about german pilots, features George Peppard
"Hedd wyn" Partially in welsh, good movie though.
WW2
"Das boot" A german film available dubbed or subtitled, about a U-Boat and it's crew.
"Stalingrad" is good, it's made by the guys that made "Das boot" and is subtitled or dubbed from the German.
"The big red one" about the US army's 1st division following it from the torch landing in algeria through europe.
"Dambusters" a solid stonker of a movie about the RAF's lowlevel attack on the dams in the Rhine valley with the "bouncing bomb" designed by Barnes Wallis. (about to be remade by Peter Jackson)
"The cockleshell heroes" about the commando attack by the British SBS on german vessels in Dieppe.
"Too late the Hero" set in the pacific campaign, Michael Caine and a team of British soldiers try and knock out a Japanese base.
"Dunkirk" John Mills tries to escape the beaches of Belgium in 1940 as the Germans tighten the noose.
"The Eagle has landed" Micheal Caine leads a group of German paratroopers on a mission to assasinate Churchill in England. (Better than it sounds)
"A bridge to far" mentioned by another poster (above), about the disasterous "market garden" operation.
"The great escape" Classic boys night in movie!
The Korean War
"Brotherhood" a Korean movie, subtitled
Vietnam
"Apocalypse now" 'Nuff said. get the redux version it explains the disintergration of the crews morale.
"Vietnam" australian movie, one of Nicole Kidmans early roles.
The falklands
"Tumbledown" about the battle for mount tumbledown on the falkland isles, 1982.
Here's one you'd love, not quite the time frame your interested in-
"Zulu" set in the 1860's and an absolute stormer of a film, Michael Caine, Stanley Baker. Based on action at Rourkes drift. The single highest number of Victoria crosses ever won in a single battle. Not historically accurate, but a bloody great film. Trust me watch it!