Why Balloons Were Used as Devices to Stop Low-Flying Aircraft Attacks During WWII

During World War II, barrage balloons became a common sight in cities and near important military and industrial sites. These large balloons were not weapons in the usual sense, but they played a key role in defending against low-flying aircraft. By rising into the sky on steel cables, they forced enemy planes to fly higher, making them easier targets for anti-aircraft guns and reducing the accuracy of bombing runs.

If a plane flew too low, it risked colliding with the balloon’s steel tether. Around 65% of such collisions ended in the loss of the aircraft. These balloons were especially helpful when visibility was poor. While most weapons struggle in foggy or cloudy conditions, barrage balloons became more dangerous because pilots couldn’t always see the cables in time to avoid them.

Stopping Flying Bombs and Protecting Cities

Barrage balloons were also used in defense against the V-1 flying bombs, one of Germany’s early cruise missile weapons. London, in particular, relied on these balloons as a final line of defense. They were credited with taking down over 230 V-1 bombs. The idea was to keep these flying bombs from reaching the city by creating a barrier of cables in the sky.

The German military had also used barrage balloons earlier in the war to protect oil facilities from bombing. But they eventually stopped using them in 1944. One reason was that Allied bombers began using the balloons as markers to locate targets instead of being thrown off by them. While effective in some cases, the German military found other defense methods more useful over time.

How Barrage Balloons Were Built

Each balloon was carefully designed to stay stable in the air. The lower chamber held regular air, while the upper chamber was filled with lifting gas—either helium or hydrogen. Hydrogen had slightly more lifting power, but it was flammable. The U.S. wanted to use helium, but most of the supply went to Navy airships. So many balloons ended up filled with hydrogen.

The balloon had fins and rudders to help it stay pointed into the wind. It also included air scoops that helped with stability. These balloons were quite large, and handling them required teams of people. Images from the time show five or more ground crew members working together to manage one balloon, especially during takeoff or landing.

Tethering and Costs

The balloons were anchored to the ground with cables and sandbags. A popular model used by U.S. forces was the D-6 barrage balloon, which was important during the D-Day landings. It cost about $9,000 at the time and was designed to stay stable in wind speeds up to 50 miles per hour.

The cable that connected the balloon to the ground had to be strong. Early versions used cables 3/16 of an inch thick, but these were later replaced with larger, stronger versions. By 1942, 1/4 inch cables became the standard. These could support loads over 7,000 pounds and were more likely to damage or destroy enemy aircraft on contact.

Improved Cable Devices and Added Dangers

Some cables were enhanced with devices to make them even more dangerous. For example, certain cables were fitted with small parachutes and cutting links. When a plane hit the cable, the system caused the cable to break apart and pull tight with force. This would saw into the plane’s wings or fuselage. Even if the plane wasn’t torn apart immediately, the sudden force could make it impossible to stay airborne.

Barrage balloons could also be equipped with explosive charges. If triggered, they could cause additional damage to an attacking aircraft. In cases where the balloon cable needed to be quickly dropped, rip cords allowed the gas to escape and the balloon to come down safely. This ensured that it wouldn’t become a hazard to friendly forces if the cable had to be cut during combat.

Effectiveness and Final Use

Barrage balloons weren’t just passive defenses. Their presence changed how air attacks were planned. Pilots had to fly higher, exposing themselves to more fire. Bombing became less accurate. And in some cases, balloons even helped bring down enemy weapons directly. While not every balloon made a difference in every raid, they added another layer of protection when defending cities, ports, and military targets.

Though no longer used in modern warfare, their role during WWII remains an example of how creative defense systems could change the outcome of an air attack.