Throughout history, military forces have come up with countless innovations in weaponry and defense. One of these inventions, which came into use during the first and second world wars, was the barrage balloon.
Barrage balloons were essentially large floating mines. They were tethered with heavy cables at low altitudes with the intent of bringing down the dive bombers that plagued enemy cities during World Wars I and II. The idea was that the bombers would collide with the cables or the balloons and be rendered useless. Some balloons were even equipped with small explosives that would pull up against the planes on impact. To avoid the balloons, dive bombers would be forced to fly higher, into the range of very effective anti-aircraft fire.
As the war years continued, the problem of barrage balloons was lessened with the introduction of high-flying bombers and aircraft with anti-balloon equipment. During WWII, Germany came up with the best cable-cutting device in order to get past the plentifully used British balloons. A device was attached to the wings of the planes, intended to catch the cables once they had been snagged by the aircraft. As soon as the cables entered the device, a small explosive charge would send a blade through the cable, freeing the plane.
As is clear from the photo above, the balloons were not entirely successful. They did slow down bomber attacks but were not able to stop them entirely. Occasionally the balloons were more trouble than they were worth. In 1942, a group of barrage balloons, tethered to protect the shipping Channel at Sault Ste. Marie near the Great Lakes, broke free during severe storms. The dragging cables short-circuted electric lines and seriously disrupted manufacturing, particularly metals production which was vital to the war effort.