In RTW you could actually recruit one brand new unit, plus retrain another eight (even if they have only one man in them) for one turn. Unleased as long as you have the money and the population for that. If ever tried to retrain an army of 19 fully depleted units, you'll know what provlem is to find about 1500man in freshly exterminated city. In MTW 2 the population is not a problem, but you can recruit or retrain 3 units at max.