The Soviets do not retreat... they fight, they die, but they do no retreat. Use the many suppression breaking abilities we gave them in order to fall back or charge.
Soviets don't have Muni costs, Muni goes towards global upgrades. This was a design choice, I dunno who the hell thought it up but it's never made much sense to me either. We are addressing the Munitions situation as well, giving the possibility that some more 'Powerful' abilities and individual upgrades should definitely have Muni costs.