I was not part of the Althing on those days, since my char was new and I wasn´t a lord yet, but from what I can remember, we were informed about was that MI had broken the treaty refusing to hand over the region, and not improving relations. And the guardians of the treaty weren´t going to do ANYTHING to fix that, so either we realized we were never getting Mansbridge and let it be, since MI wouldn´t handle it and the guardians wouldn´t do anything, or we attacked and performed a TO on the region.
That´s why we ended up voting for peace. I believe if there was a plan to wait for the treaty to expire and then attack we would have waited, improved our regions and army.
There was a plan, and Xaphan knew it, but he attacked Mansbridge anyway. Thats why Regulus hates Xaphan. Xaphan is, in the eyes of Regulus, responsible for the destruction of Norland.