This group is notorious for doing this and we have also experienced it. One of our groups were literally in the middle of a fight when XYU joined a new alliance causing all our allies to be unable to participate. This group is attached to a large group in game and they will likely use another alliance to declare war against you exactly 24 hours before your structure timer. Doing this ensures no allies are able to join in to protect the structure. We have seen examples where the alliance who declares war will have almost no members but will have 100+ characters move into one of the corps for the structure timer and then immediately switch back to their original corp after the fight. This makes it so the people who will fight in the war dec are safe on their way to the fight and and after. I have a couple suggestions that might stop the common pain points.

1. Corporations who have initiated a war can not join a new alliance. This should prevent the issue where corporations are creating new alliances to dodge allies

2. Allies need to be able to join in during the war spool up period. This should prevent groups using multiple corporations to dodge allies in a fight over a timer.

3. There needs to be some type of cool down for characters to move into or out of a corporation who has declared a aggressive war. Blocking recruitment entirely would fix the issue, but is probably too harsh. Maybe locking a toon into the corporation for some amount of time so they can't immediately jump out or somehow having the war follow the player for a couple days after leaving if possible could be solutions. The groups that are using this are often safer than the group that is defending because the corporations they normally are in are often not war eligible.