When you're sieging a tower, you have three choices: climb the wall, knock it down or hang out until everyone inside starves to death. But when the besieged have a bridge that leads to food and tower-building equipment, well then shit. So after two months of watching the tower get taller and the people inside it get fatter, the Vikings came up with a very Viking plan: fill the river with dead bodies so they could attack from every side. I assume everyone here has tried building an island out of cadavers, but I'm still going to list all the reasons this was a bad idea: screaming ghosts.
Plan B was slightly better. The Vikings lit a few of their boats on fire and aimed them at the bridge. With cheers raised to their Norse gods, the flaming Viking boats crashed into the bridge and ... and it was OK? Goddammit. If you ask me, the fact that the bridge didn't explode is thermodynamic proof that Thor is gay.