@GtotheWaveThe only rule we’re not sure about: If a joined solos stand is attacked in melee, does the solo use its own ac vs the attack too solo uses it’s AC

— Mike Mearls (@mikemearls) March 4, 2015

Sage Advice: you can download Mass Combat Rules for Dungeons&Dragons here
http://dnd.wizards.com/articles/features/unearthed-arcana-when-armies-clash