Nerve Gas

Launch nerve gas canisters into an area adjacent to an area you control.  This will kill 1/2 the armies, rounded down, in the target area or, if the wind is blowing, in an area adjacent to the target area.  Roll a die.  If the result is 1, 2, 3, or 4, the target area is affected.  If the result is 5 or 6, a randomly chosen adjacent area suffers the effect.