Board Thread:Speculation House/@comment-294840-20170719134411/@comment-26397825-20170731002412

But the train wasn't anywhere near the tunnels of Vale as it set off, it had a long way to go to get there. And the Grimm were only released into the city in that one area, and only because RWBY didn't stop the train. If they had stopped the train, the Grimm wouldn't have had a hole into Vale to enter through.

So if Ironwood bombed Mountain Glenn, he would have collapsed the roof on the White Fang operation, which included the train since Ruby got dragged past it by the White Fang guards, and sealed the entrance to the tunnel the train went down, meaning the White Fang couldn't send people down it to blow a hole in the end and open the way for Grimm. All that dust would have gone off when the train was hit by the rubble and explosions of the bombs, meaning all that would be left would literally be a smoking crater where a city used to be underground.