Cavalry and Infantry going into assault

[J6A]

Resurrecting an old thread here.  In my situation, some Russian cavalry charged some German tanks on turn 6.  It didn't go well, with the Germans rolling a "2" result and wiping out one of them, and that's not the point.  The other cavalry survived in good order.  On turn 7, 2 more cavalry units charge into the hex.  Can I add in the unit that is already in the hex AND get the cavalry charge modifier?  Or does the assault just have to be the new cavalry to get the modifier?  Based on the discussion above, I think it can be all the units, and I'm curious if others see it differently.

Although the leader for the charging cavalry is too far away to activate the guy already in the hex, so maybe not.