As it currently is, Defensive Pact is broken. There are three core issues with it: 1. The AI doesn't understand Defensive Pacts. They are eager to accept pacts with their friends without paying much attention on factors such as whether this friend is actually capable of defending them in the event of war, or whether the friend is likely to need defense themselves. The AI should avoid defensive pacts with weak civs that are likely to be attacked and prefer defensive pacts with strong civs that are not likely to be attacked. Furthermore, based on some rather quick DP-inspired wars between me and AI players, the AI doesn't take defensive pacts into account when deciding whom to invade, even though it should know about them. 2. The diplomatic penalties from obeying defensive pacts are unjustified. If I make defensive pact with Pedro, and Alexander attacks Pedro, I automatically declare war on Alexander and face the warmonger penalties. Alexander is the aggressor and knows about the defensive pact, and thus knows that in committing himself in hostilities against Pedro, he also will attack me. The diplomatic penalty should land on Alexander for attacking, not me for just obeying the defensive pact that was intended to ward off conflict anyway. 3. The Defensive Pact is an empty promise. "If a signatory to a Defensive Pact is attacked, the other partner is automatically at war with the attacker." That's all there is to it. The pact's promise is fulfilled by a simple declaration of war, with no real hostilities needed, making it rather useless for mutual defense if the other signatory doesn't bother to show up. The AI, I believe, is programmed to play fair and actually wage war against the aggressor, but human players have no such obligation and never get called out for not actually participating in the war, making the system unfair against the AI in single player and nearly useless in multiplayer. Surely, if the pact's purpose is mutual defense, there should be some actual defending involved? Fixing number two shouldn't be hard: just alter the declaration of war so it's Alexander who is declaring war against me, not vice versa. Number one may be more difficult, but I believe it would still be fairly straightforward to work out a decent set of values for the AI to consider when thinking about Defensive Pacts. Number three, however, is one that I haven't figured out a simple solution for yet. Any ideas? Comments?