Ok, I am hanging about near The Honning Brew Meadery, along with my follower, Uthgerd, when suddenly 3 legion soldiers walk by with a stormcloak prisoner. I leave them be as they head towards Whiterun, whilst I kick about the area doing some butterfly catching. Now, I decide to catch up to these soldiers after my muck about and have a chat, which simply results in the soldiers warning me to leave them to their business, instead, I leave my guy standing idle in front of the stormcloak, which results in the legion soldiers drawing their blades and warning me to leave or they'll resort to violence. Now, to my amazement, they engage me, which results in every nearby whiterun soldier drawing blades and attacking us too. I quickly free the Stormcloak and find Uthgerd and the prisoner fighting the soldiers, who quickly surround us. There's at least 10 soldiers vs us 3 here. The prisoner is quickly killed and Uthgerd holds her own before being killed, after taking 2 soldiers with her. At this point, I have killed 1 Legion soldier and used a lot of health potions to soldiers hitting me with blades and arrows. I decide to retreat towards Whiterun, which results in the guards there coming after me, so I pop inside. At this point, I have about 8 soldiers follow me in, then the rest of the soldiers there come at me. I decide to quickly hire the mercenary in the tavern, who then joins the fight, but here is where this really takes off. I flea up towards the residential area, and by this point, around 20 soldiers are engaging me, firing arrows and swinging swords like crazy. I figure this is the end since I'm taking massive damage and potions are running low, but suddenly, Companions swarm the area. I couldn't believe it. I had every companion that was hanging around Jorrvaskr draw blades to engage the soldiers in my defense. Theps to Jorrvaskr and the ring surround the tree was a site to behold here. Even more Companions came out from the rear of the building and sprinted round to join in the fight. My hair was standing here. It was immense!!! Did I mention the Battleborns joined in too? This was incredible, seriously!

Sadly, I realised, that despite the soldiers being the aggressors, killing them resulted in bounty and fines, so I decided to reload my save and leave those legion soldiers alone. If you wish to recreate this, you must allow the legion to engage you for themselves by standing and looking at the Stormcloak. If you free him first, for some reason the whiterun guards just watch the fight and let you get away with killing the soldiers. You cannot be the aggressor, or your followers will engage you instead of fighting beside you. As for companions, they seem to defend you regardless, since when I recreated this fight, I struck a soldier deliberately, yet they still stormed to my defense.

Happy fighting. Oh, and don't sheath your blade or the fighting stops. If you stop the fight before striking any whiterun soldiers, you can get away with the killing of the legion, despite the whiterun soldiers seemingly taking their side.

Anyway, sorry for the very long read. Enjoy.

OK SERIOUS GLITCH DISCOVERED. PLEASE DO NOT SAVE YOUR GAME IF YOU EVER WANT TO RECREATE SOMETHING LIKE THIS BY ATTACKING GUARDS FIRST, OR YOUR COMPANIONS WILL APPROACH YOU AFTER AND ENGAGE IN CONSTANT DIALOGUE, IN THE SAME WAY GUARDS DO WHEN APPROACHING FOR AN ARREST.

You cannot avoid this if you do it this way, it seems. So don't do this and save, only do this for a fun big fight, involving every city guard vs you companions and followers.