Once war is officially declared between two countries, the real trouble isn't the war itself, but the enemy and ally relationships in the international diplomatic arena.
On the surface, everyone has signed all those numerous messy treaties and agreements, and once war is declared, the clauses in these agreements will take effect. At that time, deciding which side you stand on and whether you're willing to acknowledge past debts are all matters to consider.
So it goes for nations, and the same applies to the Jianghu World.
Just like when the six major sects besieged the Bright Summit back then, you claim to be a reputable sect, so now that our Ming Sect wants to rise against the Yuan dynasty, what does your siege on us mean?
The Sanhe Society and the four major halls are currently in such a delicate relationship.