This happened a few years ago, a fox incident involving my Delaware rooster and two of his sons (Barred Rock mothers). All three males were very friendly, but they knew what to do to work as a team when confronted with a predator.
https://www.backyardchickens.com/th...-progress-thread.784466/page-15#post-12265136
https://www.backyardchickens.com/th...-progress-thread.784466/page-15#post-12265136
Not sure just how it went down with the chickens as I didn't witness the main event...but they weren't real old at the time either so I'm sure that would have played a part in how they reacted. Luckily the fox only managed to get one of my Black Australorp hens before I was able to intervene...and then fox met his demise. 
