Attack: N
N = 50 - #Enemy recruits
Enemy recruits: -N
So if your opponent has 50+ recruits, this card does nothing? Odd for a Rare. Also interesting is that the most it can reduce the opponent's recruits is 25.
I wonder if it was actually intended to be Enemy recruits -50 rather than -N. That way, you'd be burning as many as 50 recruits and attacking equal to the overage.