Shooting down an observation balloon was harder than it sounds. They were heavily protected by antiaircraft guns, and often by enemy fighters as well. Even though the balloons were filled with hydrogen, incendiary (tracer) machine gun bullets tended to go right through them without igniting the hydrogen. A French pilot named Le Prieur developed an incendiary “skyrocket” that could be electrically fired from an airplane. They were very effective, if they hit the balloon. They tended to twist and turn like a 4’th of July bottle rocket so their maximum effective range was about 100 yards. Even then, it was best to fire them straight down. So, the pilot had to dive straight down toward a balloon, wait until he was within a few seconds of colliding with it, fire the rockets, and pull out of the dive. Norman Prince talked Capt. Thénault into getting some rockets for him to try. He didn’t have any success with the rockets, and he flipped the plane while landing. (Photo courtesy of Washington & Lee University.)