Sounds like Linlithgow a few years ago. The lack of bobbies led to the "youngies" taking on the oldies ie teens early 20's took on the late 20's early 30's after a bit of a falling out do. The police force at the time was 5 and let the battle go ahead with a warning that the LIvingston and Falkirk support would be there in about 15 mins.

They couldnt stop it so stood back and let it happen