If I recall correctly, we were starting a round of diplomacy, big population, no variable units. Random territories deals me the European card, alright in default games but less fun in diplomacy if the trans-Atlantic alliance breaks. I start chatting with people in private chats, ensuring that we have mutual peace agreements. Africa dropped early and is happy to keep the Mediterranean peaceful to concentrate his bomber waves on South America and Asia.
Suddenly Russia drops and I fear the worst, but luckily he placed most of his fleet by Asia. I convince him to not attack me and to do a cease-fire (well he did at least...). My Asian alliance mate is getting beating up badly but the North American is doing ok in the fight against the now united South America and Africa. I hold my fleets back and move my pieces into play. I manage to squeeze a group of subs between South America and Africa (so they can hit Sao Paolo and Kinshasa), the other group is parked near the Caribbean to cover New York when the time comes. The other six are placed near Russia to keep the reds under control.
Too make a long story short, I manage to convince Africa and Russia to not attack me until a good way into the victory timer, where I launch a massive bomber/sub wave at Russia and Cairo and do a cross-launch at Sao Paolo and Kinshasa. In the meantime my Atlantic subs incinerate New York. Before either team can react, victory timer runs out and the backstab won the day.
I must admit, there were some not-so-happy campers and I had some backlash (in another game
) but it was totally worth it 
Cara
P.S. To all my fellow back-stabbers, don't backstab people unless its to win. If you can't win, don't backstab, it ruins the clientel.