Time Traveler Conversation - Doctor Who

How can you tell a man who had just went through hell, who firmly believes that this is where humanity should be disgusted of war and conflict for good. Be told this wouldn't be the last time humanity would go to war on such grand or greater scale of battle, but also that the sequel is just around the corner.

Would he even react to "World War" specifically? It wasn't known as anything beyond the Great War for sometime afterward, right?