The rule on truces is; there is no rule on truces.
If you would like a guide to go by, it would be wise to think of a truce much the same as you would an armistice, cease fire.
Having a truce does not mean you can (or should) leave your (flank unguarded) borders vacant.
A truce can be a save all or break all.
Players will use it to there advantage (and should)...better win if you break a deal!
I would guess, a player (good player) that breaks treaty's has a greater win percentage than a player that does not (ever) break treaties.
Use a treaty to gain an advantage, not just a save all situation.
I was just in a game where somebody requested a ''little'' truce.
I did not respond; I pulled my units off of his border...in so doing he thought that was enough; acknowledging the commencement of the (requested, not confirmed) truce?
Two turns later he was sweeping the board, naturally I attacked.
Of course he started bitching (rating of 4.0) about me being a truce breaker?
There is no declaration when you have an unspoken (even if only 'one' party decides to speak of truce) truce.
Many risk players do not like or understand diplomacy.
Watch whom you make a treaty with.
Don't make treaties if you are not set up (thinking, prepared) for a backstabbing.
Treaties serve two purposes...peace or surprise attack.
Try to be the first one to break a truce...that way you should always be prepared.
truces (cease-fire; armistice) are never meant to last.
If a player has more than three backstabbing (boxes marked) in his ratings, do not even consider him a candidate for a truce (unless you have a good position to backstabb him)
I try not to beak any truces that I might make.
I might be inclined to make ( 'break' ) a truce when somebody else purposes a truce (depending on his current rating), Knowing he is up to no good.
If you can, go for an unspoken treaty (understanding) these are not meant to last and you do not have to declare them in chat (keeping silent).
Many players out there do not like it when players make (purpose) treaties...in so doing you might be provoking them.
If somebody proposes a truce, go with it (if you like) but say nothing.
I was playing a game where my neighbor and I had been peaceful the entire game (about 9 turns), then he decides to mention truce (in chat), I said nothing ( I did not attack him). He then attacked me, makes no sense, he knew I was friendly.
I them proceeded to go up in him!
I am sure he wanted more of a secured sense of protection (his requesting a treaty). When I did not respond (I felt declaring a treaty in chat would hurt my position) he decided that (my silence) was an act of aggression (I guess).
Point being; Learn how diplomacy works, read your opponent.
Attacking right after you request a truce (makes no sense what so ever) is much the same as breaking a truce...even worse!
Diplomacy ( truce, treaties) has different meaning (understanding) for all players involved. I can guarantee that every player involved in a truce is looking, searching for a loophole in order to screw (any reason to break the treaty...justified by them) the other guy.
Some know how to use it (diplomacy) others do not. Many players will not even consider mastering it (diplomacy)...yet they use it...much to their own demise.
Diplomacy is a must on some of CC game boards.