40k multiple assaults question

[mallet_man]

So playing a game of 40k last night, my friend had a unit of guardsmen in close combat with the Avatar, they were surrounding him, so no other units could move into base contact with him for a new assault.
He then wanted to assault the Avatar also with a bigger unit of guardsmen and thought that he could just join the back of the other unit as long as he had models within 2" of models already in base contact with the avatar, I told him I thought it was wrong as it was a new unit they had to get models into base contact with the avatar to assault him, but I could not find anything in the rule book under multiple close combats to justify this! Anyone know any page references or exact rules about this?

Thanks

MM

[MasterSlowPoke]

The closet assaulting model assaulting has to get in base contact with the closest enemy model for an assault to work. If you can't get anyone in base contact, no assault.

Furthermore, the 2" rule only applies to models in the same unit.

[mallet_man]

thats what I thought thanks for the confirmation :)