My two favorites are John Keegan ("The Face of Battle", "The Mask of Command", "The Price of Admiralty", "Six Armies in Normandy" and two excellent single volume histories of the First and Second World Wars) and Alistair Horne ("How Far From Austerlitz?", "The Fall of Paris, 1870", the "Price of Glory" [about Verdun], "The Fall of France 1940", and "A Savage War of Peace" [about France and Algeria in the 1950s]).
Horne assumes a great deal of background knowledge on the part of the reader, and also has an irritating habit of inserted untranslated phrases in French which have me wracking my dim memories of college and high school language classes. He is also a dedicated Francophile (which makes you wonder why he only writes about the most gloomy events in French history).