Alright, here are the rules (they are subject to objection).
1. All Alliances, Declarations of War, Public DMZs, and Truces must be announced globally in order to take effect. If any party involved in the announced agreement takes offense to said agreement, the agreement will be considered null and void.
2. Any power, in order to attack another, must first declare war with that player a DIPLOMACY turn in advanced. As this is always, to some extent, a rule that allows for confusion, allow me to clarify what an attack is:
a. If you order your unit to enter another player's territory. Whether the move succeeds or fails, you must declare war prior to making this attempt.
b. If you support a unit into a neutral territory that is being occupied by another player and you dislodge the other player's unit.
c. It is not an attack if you attempt to move a single unit against a neutral territory, either bouncing or bumping another player's unit.
d. It is an attack to violate an established DMZ between you and another player, unless the DMZ is not announced globally.
3. In agreements of alliance, any power within the alliance must be at war with any enemy of the alliance. If the otherwise neutral alliance member refuses the declaration of war, their alliance is to be voided.
4. Any power who violates the rules by attacking another player or by violating a public DMZ will be forced into suspension for one year or two Diplomacy phases (during which time, retreats may be entered, but not orders or builds).
Here's an example of a game:
S1901
France and England, DMZ English Channel
Germany declares war on France (Germany may attack in the Fall)
Austria declares war on Italy (Austria may attack in the Fall)
Italy and Turkey sign Alliance
Turkey and Russia, DMZ Black Sea
F1901
England declares war on Russia (England may attack in the Spring)
*Germany attacks France*
*Austria attacks Italy*
Turkey declares war on Austria (as per alliance, may attack in Spring)
Russia violates DMZ Black Sea (May not build in Winter)
S1902
France and England sign Alliance
*England attacks Russia*
Austria and Turkey sign Truce (Italy-Turkey Alliance void)
Turkey declares war on Italy (Turkey may attack in the Fall)
Turkey declares war on Russia (Turkey may attack in the Fall)
Russia: SUSPENSION (May not issue orders)
F1902
England declares war on Germany (as per alliance, may attack in Spring)
Austria and Turkey sign Alliance.
*Turkey attacks Italy*
*Turkey attacks Russia*
Russia: SUSPENSION (May resume orders with builds phase)