The recruit defection mechanism was not thoroughly tested and balanced, was it? It is very unfortunate. If I have a recruitment citadel disadvantage, any recruits gained through conquest of sites or sale of structures immediately goes to the other side; at least sooner than I can allocate them to the construction of a recruitment citadel. While I have enough power on the map to win without new units, it is really annoying that every bit of progress I make will supply the other side with fresh recruits.
And once you're in that situation, you're bound to hit 0 recruits, and then there's no way you're going to do all it takes to get 20 and use those 20 before they're gone.
They want the recruitment citadels to serve some purpose after the population has been depleted, right? Maybe they shouldn't. IF they are to be useful when there's nothing to recruit, maybe let some recruits come in still, but only to the side with most recruitment citadels, and at the rate of a single recruitment citadel only. (If sides tie for highest number, they share the recruitment; 2 sides get half rate)
I'll complete the battle, but how painfully slow this recruitment drain made it!
