I am unaware of many of the particulars involved here however...
I find it amusing that many in this thread think suggesting there is a proper way to declare war is some kind of joke.
Cause well, there is a proper way.
If you do not do so then you are, by definition, a backstabber, and not to be trusted. As for gaining a diplomatic agreement to be able to travel through ones lands and then using that as a means to attack someone, this is even worse. Do the HRE actually believe that other factions will afford them this privilege in the future?
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Of course this is a beta, it is a game, but people have memories. I guess what all you factions do to their own reputations is their business, and the Mercs did some fine work. Cannot really say the same for all those others involved though.
Anyway an entertaining war it seems. Congrats to the mercs I suspect you have done better than many expected.