Operation Outward was a military program carried out by England to attack Germany using free-flying balloons. They were filled with hydrogen and carried either a trailing steel wire intended to damage high voltage power lines by producing a short circuit, or incendiary devices that were intended to start fires in fields and forests.

Althought english military carried out studies to asses the extent of damage caused by a rogue barrage balloon hitting power lines as early as 1937, the idea behind the program was born during the "Battle of Britain". On September 17, 1940 a raging storm with gale-force winds ripped from their moorings, many of the barrage balloons which defended english cities from the incessantly Luftwaffe bombings. The balloons were carried by the winds over the North Sea toward mainland Europe, dragging their severed cables behind them. In a matter of hours, reports of electrical outages in countries like Denmark, Sweden, and Finland began to spread. The balloons' heavy tethering cables had struck high-voltage lines, short circuiting them and causing power outages which affected from electrified railroads to whole cities.

Britain's leaders guessed that the damage caused by the rogue barrage balloons could be turn into a purpose-designed and deployed system able to cause such a damage to Germany's electrical infrastructure. That was the genesis of Operation Outward.

The British military rightly assumed that balloon attacks would be very hard and expensive for the Germans to defend against. The balloon cruising altitude was high enough that even during daytime, they will be forced to divert their fighter aircraft to intercept and destroy the balloons, with an additional waste of fuel, and other precious goods.

After struggle between opponents in the Air Ministry and proponents in the Admiralty, the British Chiefs of Staff gave the go-ahead for Outward in September 1941. A launch site was set up at HMS Beehive, a Royal Navy shore establishment near Felixstowe in Suffolk. The launch area was located at the Felixstowe Ferry Golf Club. More than 230 men and women from Royal Navy, Royal Marine, Women's Royal Naval Service, the RAF Balloon Command and the Naval Meteorological Services were assigned to the operation. For security puroposes, the launch crews acted under the cover story of being part of a "Boom-defence" unit.

The balloons used were surplus weather balloons -which where in large amounts in Royal Navy's stock- measuring 8 feet in diameter when inflated. They carried a simple timing and regulating mechanism: at launch, a slow-burning fuse was lit; its length was calibrated to the estimated time to arrive over German-controlled territory.

The balloons were inflated using hydrogen from pressure cylinders inside three-sided tents or windbreaks. To avoid hydrogen ignition due to friction between the balloon and the tent canvas, during inflation, the latex was keep wet with a water spray. The inflated balloons were conveyed by hand to a dispersal point, where their payload was attached.

Two kinds of "payload" were used in the balloons: a trailing wire or an incendiary device

The trailing wire consisted of about 700 feet of 1.6 mm diameter hemp cord with a breaking strength of 40 pounds, which was attached to 300 feet of 1.8 mm diameter steel wire. The plan was that the wire tail would be dragged for about 30 miles across the countryside and eventually encounter a high-voltage transmission line and a phase-to-phase short circuit would be initiated.

The incendiary devices were of different kinds. The so called Beer consisted of a cylindrical metal container 22 cm in diameter and 23 cm long containing seven or eight half-pint bottles. Each bottle was a special incendiary grenade called SIP composed by white phosphorus, benzene, water and a strip of raw rubber, 5 cm long, which dissolved and formed a layer. After a delay caused by a slow burning fuse, the metal container was tipped open and its contents allowed to fall out. On shattering the SIP grenades would spontaneously ignite. Jelly were cuboid cans that measured about 290 mm x 170 mm x 100 mm and contained 4.5 liters of incendiary jelly. A release mechanism and a fuse were provided, on ignition a fireball erupted with a radius of about 20 feet. Socks were long thin canvas bags of incendiary material each weighing about 6 pounds, packed with wood wool, bound with wire and soaked in boiling paraffin wax. Each Outward balloon could carry three socks and when dropped, socks formed a V-shaped sausage designed to catch in the crown of a tree. Fuses were inserted in each end of the device and it would burn from each end for 15 minutes.

Once launched, the balloon rose rapidly and expanded in size until an internal cord tightened and preventing further increase in altitude beyond 25,000 feet by releasing some gas; the balloon would then begin a slow descent due to the hydrogen gradually leaking away. After a while, the slow burning fuse would release a bung in a can of mineral oil; as the oil slowly dripped out, the balloon's payload would lighten, arresting its descent. The same slow-burning fuse was also used to release the balloon's weapon.

The first balloons were launched from Felixstowe on 20 March 1942 and within days, the British were receiving reports of forest fires near Berlin and Tilsit in East Prussia. In July a second launch site was set up at Oldstairs Bay near Dover and by August launches from both sites reached 1000 balloons per day, and later increased to attacks involving up to 1800 balloons all launched over a period of three to four hours. The operation continued at this pace for months, though they were frequently suspended when there were large air-raids on Germany as it was feared the balloons might damage Allied bomber.

From May 1944 it was decided to change tactics because of increased allied aircraft activity. The mass balloon launches were stopped and replaced with a "trickle" of balloons launched from three sites at ten-minute intervals throughout daylight hours. This scheme was maintained until last launches which were performed on September 4th, 1944.

During the 899 days that endured the offensive, a total of 99.142 balloons were released.

In all, the operation was very succesful. The harassment value on German air defences alone justified Operation Outward as it cost the Germans more, in terms of fuel and wear and tear on aircraft, to destroy each balloon than it cost the British to make them. After the war, German records revealed that the trailing wire attacks had caused considerable inconvenience with electricity supplies regularly being interrupted and significant damage to the electrical distribution network. Ones of Outward's greatest success occured on July 12, 1942, when a wire-carrying balloon struck a 110,000-volt power line near Leipzig: the failure in the circuit breaker at the Böhlen power station caused a fire that destroyed it.

Althought the effects of the incendiary attacks were very difficult to assess -to tell whether any particular fire was caused by Outward or by an accident, sabotage, or aircraft-dropped incendiary- reports from newspapers printed in occupied Europe indicated that some fires had definitely been caused by the balloons.