Is there a specific situation in which a defensive pact is null and void? I'm almost finished with a crazy fun game where the Incans became the dominant superpower. I made DPs with Brazil and Morocco, and once I felt it appropriate, I began to poke at the Incans until they declared war. My 2 vassals, my CS allies, and Morocco went to war with them, but Brazil managed to stay out of it somehow.
2-3 turns later, Inca bribed Russia to DOW me, and brazil, morocco, etc all went to war as they should, so I thought maybe this isn't a bug? This is the 12-13 version.