April Morning by Howard Fast. It's about April 19, 1775 told from the point of view of a young teen standing against the British at Lexington and Concord.
The books by David L. Robins a fictional history set in WW II as told from people on both sides of the fighting.
War of the Rats about the battle of Stalingrad told from snipers point of view.
The End of War about the Russian advance into Berlin.
The Last Citadel about the battle of Kursk
Liberation Road about the Red Ball Express the logistics battle in keeping the US soldiers supplied as the advanced across Europe.
I'll also recommend anything by David Drake. He does military science fiction.