Getting quite frustrated using it, as it is not helping you to break through the second layer.
drop a pair to break first layer, done. Next, drop another pair hoping will break 2nd layer, but it went to break another first layer a distance away.
drop the 3rd pair, it went to the other corner to break it. Damn..... looks like you just need to bring just a few to break first layer, and let other troops to break the other layers.

