Why destroy Laketown's bridge?

[Rikae]

Good points, Sixth, just one thing I'd like to mention:

Originally Posted by The Sixth Wizard

The Hobbit reads "the bridge was thrown down and destroyed." I personally would presume it was by burning. Although "thrown down" appears to indicate it was ripped apart, Tolkien uses the word "destroy". If it was ripped down, Tolkien would have used words like "broken" instead, which seems to me to indicate it was burned. It would certainly make sense.

I think this description fits quite well with the suspension-bridge scenario - the bridge could be both "cut" and literally "thrown down". When the bridge is also "destroyed", it could very well be that it was first cut loose, then set on fire (setting it on fire without cutting it loose first risks setting the city on fire as well).

I would imagine the bridges probably had guards posted and these guards, during their initial training, were taught the emergency bridge-destruction plan, shown where the tools were kept and which ropes to cut if the signal was given, something of this nature. Even in the absence of guards, those who lived and worked near the bridges would have been similarly prepared. If the villiage is small enough, everyone might have known said emergency plan and been prepared to execute it.