Anyway, they spend the whole season building up how the Japanese home islands are a fortress, and the Japanese will never surrender, and there's no way to take the Japanese home islands because they're invincible...and then they realize they totally can't have the Americans take the Japanese home islands so they have no way to wrap up the season.

So they invent a completely implausible superweapon that they've never mentioned until now. Apparently the Americans got some scientists together to invent it, only we never heard anything about it because it was "classified". In two years, the scientists manage to invent a weapon a thousand times more powerful than anything anyone's ever seen before - drawing from, of course, ancient mystical texts. Then they use the superweapon, blow up several Japanese cities easily, and the Japanese surrender. Convenient, isn't it?

So yeah. Stay away from the History Channel. Unlike most of the other networks, they don't even try to make their stuff believable.