Maps of Military Encounters from Ancient to Post-Roman times

"Atlas for Ancient Warfare"
West Point Academics

A good collection of maps, including "The Persian Empire, 490 B.C.," "The Battle of Thermopylae and Movements to Salamis," "Routes of the Barbarian Invaders, 4th and 5th Century."

There's not much in the way of bells and whistles, but it's a good information resource.