A GL NAP has simply declared that they will not wage war with the other party for the entirety of the Campaign although NAPs can sometimes evolve into Alliances, but they are two very different Diplomatic Entities.

An alliance may be between 2 players or even several players within a game, it may have goals like trying to get all players within the alliance into the purse for instance.

If you do find yourself needing to cancel a Nap to assist an Ally or for any other reason for that matter, here is how the process works.

In the case of a 3 tick Nap, Termination must include a three cycle warning period before movement orders are given.
As an example, if warning is provided on cycle 15, movement orders may be issued on cycle 18.
As seen above, the orders may be issued on the third cycle of warning, however, the battles will not be able to be viewed until four cycles after notice of cancellation is given.
For the most-used definition of a NAP, please follow this link.
http://www.madnergal.com/en/oldelrads/Scrolls/NAP3.html If you've any questions on NAPs or Alliances, please do not hesitate to contact me.