this is the first time anyone has made any organized effort to use adventurers in war
organized effortAnd this is where the true problem lies in my opinion.
Was this accomplished OOC?
That is cheating and the involved parties (and only them) should be punished IMO.
More likely this attack was accomplished by a group of guild members working together, which is currently allowed and acceptable IG.
Maybe a more effective way to deal with this would be to prevent guilds from including commoners.
Why would any noble want to be in a guild that included commoners, other than to control those commoners?
To my knowledge, guilds are the only effective IG method of organizing many commoners to a common goal.
A single Lord may be able to rally a few commoners to their cause, but there is always a chance that they will contact "the wrong commoner" and have their plans disclosed to "the wrong people".