which was overlooked by Gaustatoppen, a mountain approximately high; the plant itself had been built on a broad rock shelf above the river bed. Einar Skinnarland had observed the German defences over the summer and passed the information back to SOE. Later reconnaissance by Torstein Skinnerland and the Grouse team was also transmitted to London in the weeks leading up to the operation. In early October Generaloberst Nikolaus von Falkenhorst, the commander in chief of the German forces in Norway, had visited the plant. While there he warned the local garrison that he believed the plant was a likely target for British commando raids, but crucially he did not have the resources to increase the manpower there. Although Einar Skinnarland had observed a garrison of 100 men in the village of Rjukan, 20 at the dam and about 55 near the main plant during the summer, by October this had been reduced to about 12 at the plant, 12 at the dam and approximately 40 in Rjukan. Most of the men were elderly or infirm Austrians under the command of an elderly captain, although well trained German regulars periodically passed through Telemark. Skinnarland also believed that Gestapo agents were in the area. The Germans had erected three iron hawsers across the valley to prevent low flying bombing raids but on the ground most of their defences were positioned to prevent an assault from the ridge above the plant, the direction from which they believed an attack was most likely. Minefields and booby traps predominantly protected this side of the plant, but there were also searchlights on the roof and a machine gun nest near the entrance. A single bridge crossed the steep gorge in front of the plant, but was normally only protected by two guards. There were 300,000 German troops in Norway at this time and reinforcements could quickly be called into the area, which would complicate the commandos' escape to the Swedish border. Planning The Headquarters staff of Combined Operations at the War Office was tasked with devising a plan for the glider-borne assault on the plant, as it had been with previous airborne and commando operations, such as Operation Biting. This was the first British airborne operation ever to use gliders; all previous operations had been conducted solely with parachutists. The staff decided that although gliders would be the most suitable for the operation due to the