Flechettes, to use the technical term, were used extensively and somewhat successfully as an anti-infantry device, and also less successfully as an anti-zeppelin device. The idea was that just by dropping them en mass (boxes contained up to 250 darts, and multiple boxes could be carried on a plane) overhead, the darts would gain enough speed to punch through helmets and gas envelopes and kill the unfortunate person or airship below. While this worked out with human targets, a zeppelin's envelope deflated too slowly to kill an airship. Incendiary bullets proved much more effective against airships, while bullets and bombs proved more effective against infantry, especially once forward-firing machine guns became functional.