Back when it was not uncommon to lose every officer in a battalion in a battle

I've been reading Six
Weeks: The Short and Gallant Life of the British Officer in the First World War,
by John Lewis-Stempel. I bought it in a store in St. Ives, Cornwall, on a
stormy day when the tops of the gray waves off the Irish Sea were hitting the
slate roofs of waterfront houses in the town. (But in Doc Martin,
wasn't Cornwall always sunny?) 

One thing that has really struck me in the book is how often
battalions would lose many or even all their officers in a battle. "I ended up
the only officer in the battalion," wrote 2nd Lt. Stuart
Cloete, who was 19 years old. Of the 30 officers in one battalion of the
East Surry Regiment who went into a battle on the Somme, four came back.  And the 6th Battalion of the
King's Own Scottish Borderers lost every one of its 20 officers in an attack on
September 25, 1915. If I recall correctly, Robert Graves wrote in Good-bye to All That that as a
lieutenant he went on leave and returned to find himself the senior surviving
officer in his battalion.     

I also was struck by the narrowness of military history in
the small bookstores I visited in Cornwall. Basically, they are about the
British in the two world wars, with a soupcon of the Falklands and Iraq tossed
in. I can understand not paying much attention to the Americans, but how about
ancient history at least?

And has anyone read Emperor Maurice's Strategikon?
Worth reading?