I think many players doesn´t know about this trick. When you take a capital your morale goes up 10 % everywhere and with that recruitment becomes more frequent. This everybody knows. But this only updates at day change so if you take a capital you have to wait until new day before your recruitment speeds up. The trick is that there is a way to reboot your recruitment centers so that the speed-up happens right away and this act only take you 3 seconds to do for your whole country.
It´s under 2 minutes long and well worth watching. You will learn how to recruit faster after taking a capital in the middle of a game day.