Many a friendship has been damaged after a brutal game of Diplomacy. There are gamers in my circle of friends that will never play it again. A game for great Poker players!
Diplomacy was a great game, I played when I was in high school with my parents and a couple sisters. I had a similar story with Risk. My dad was a big wargamer, and taught us early. I played most of the AH games, but Diplomacy and Risk were games my sisters could get into also, and really needed more players.
We were playing a game of Risk, and my mom had made a deal with my sister for an alliance. But my sister got a match, and (with some prodding) decided to take my mom's last few territories to get her cards. My mom was TICKED. She got up and said that was fine, she would go make dinner anyway. About 20 minutes later, she brings in hamburgers for all of us, except my sister (who was still in her early teens). We thought she was just being funny, and left her burger in the kitchen, but nope, no burger, pans put in the sink, nothing. My mom told her she could make her own sandwich.
Do NOT cross your mother in a wargame!!