I saw a very interesting TV documentary about World War One Zeppelin raids a few weeks ago.
They were trying to figure out why it was so difficult for contemporary fighter planes to shoot them down. You'd think that a big, slow-moving bag of hydrogen would be just the most vulnerable thing in which to go to war, but it turns out it was surprisingly hard to set them alight. Regular bullets would pass right through the internal gas balloons and the airships would survive the resulting slow leaks. Even specially developed burning bullets didn't work, as they couldn't set light to the hydrogen in the absence of oxygen. The eventual solution was to equip the fighter planes with magazines containing a mixture of burning bullets and exploding bullets. The exploding bullets would tear bigger holes in the gas balloons, so that enough air would mix with the hydrogen for the burning bullets to start a fire.
The other thing which surprised me was that the gas balloons inside the Zeppelins were made out of huge numbers of cows' intestines - about 200,000 of them were needed for every airship. This heavy demand eventually resulted in a national shortage of cow's intestines, so in order that the assembly of Zeppelins wasn't held up, the German authorities banned the production of sausages.
-R