Military Alliances, Defense Pacts and Non Agression Pacts

Military Alliance
The top tier of international diplomacy. Military allies can be called to offensive wars and defensive wars. Being allied with someone allows you to move troops through their territory. Breaking a military alliance causes a long [288 years] truce.

Defensive pacts
The second tier of international diplomacy. Unlike military allies defensive allies can't join offensive wars and you can't move troops through their lands. They however join automatically in any defensive war that is declared on you. Breaking a defense pact causes a short [25 years] truce.

Non Aggression Pact
Lowest tier of international diplomacy. Having a non aggro pact with someone causes you to be unable to attack / be attacked by said person. You can't move troops through their territory and breaking the non aggro pact causes a medium [144 years] truce.