Five other words sufficed to explain everything:

"Civilians fired on our troops."

Not one village in flames, not one desecrated monument, not one
organized killing, not one tortured city that does not fall under the
scope of one or the other of those justifications, "War is war," or
"Civilians fired on our troops."

Doctors, savants, officers, Bavarians, Saxons, and Prussians have
adopted the double excuse with a marvelous unity: they advance it in a
certain tone of voice. It is firmly embedded in what is left of their
consciences as firmly as the iron cross is riveted on their necks.

Besides, it was all planned, wished for, arranged in advance. German
frightfulness formed a part of the plan of campaign. It is enough to
read the manual called "Kriegesgebrauch in Landkriege" (Military
Usage in Landwarfare) to be very much edified. Every German officer
has had this manual in his hands since the days of peace. It comprised
his rules of warfare. It was a part of his war equipment, the same as
his field glasses and his staff-officer's card. And here is what he
reads on the very first page:

War carried on energetically can not be directed against the
inhabitants and fortified places of the hostile state alone;
it will endeavor, it ought to endeavor to _destroy equally
all the enemy's intellectual and material resources_.
Humanitarian considerations, that is, consideration for the
persons of individuals and for the sake of propriety, can
have no recognition unless the end and nature of the war