... Wait, what? This was a villain twist that was only surprising because it does not make any sort of logical sense in the movie. It's confusing that he would be supporting an armistice (although he suggests in his dialogue with Diana that it was just to make the British drop their guard). It also makes Ares responsible for putting Diana in the perfect position to end all of his plans, making him seem extremely short sighted.
Or was he? I was upset with the Hollywood twist of having the man who is proposing an armistice turn out to be the god of war. However, then I remembered that the armistice would lead to one of the more lopsided treaties in history: the Treaty of Versailles. This treaty would blame the Germans for the entire war and put such crippling restrictions on it government that a generation later would see the rise of the Nazi party, and thus the even more destructive World War II, as a direct result. Suddenly, Ares' hands in the armistice makes a great deal more sense. Sure, he was bringing about the end of one war, but in doing so, he was creating a war much more terrible.
I suppose the twist actually makes a lot of sense.
*There was an actual General Ludendorff in history. Like the movie, he was in charge of developing chemical weapons (and promoted the use of mustard gas in combat). Unlike the movie, he did not die in WWI having been impaled by Diana. Rather, he recommended the armistice (under more favorable terms), was blamed for how it turned out, and forced to go into hiding. He later came back into power by blaming all of the changes to the treaty on the treachery of Jews, Christians, and Freemasons. He would support HItler and influence some of his political ideas, but would later distance himself from him because Ludendorff did not feel that Hitler had the military acumen to actually conquer the world. He died a couple of years before the invasion of Poland.