When the Nazis’ quest for a nuclear weapon began in earnest in 1939, no one really had a handle on how important nuclear weapons would prove to war and geopolitics. The attacks on Hiroshima and Nagasaki in August 1945, along with the Cold War-era tests and their accompanying mushroom clouds, would demonstrate the true power and terror of nuclear weapons, but in the late 1930s these bombs were only vaguely being thought through, particularly after the successful first experiment to split the atom by a German scientist. The nuclear age itself was in its infancy, barely 35 years old, but within a few short years the advent of nuclear war loomed over the world and the prospect of a malign dictatorship winning the nuclear race kept Allied leaders awake at night.

When the Allies learned the Nazis had a heavy water plant in occupied Norway, they considered various ways to stop it. Bombing raids by the Royal Air Force (RAF) were not practical since they lacked the required accuracy, so it seemed that the only way to slow down or stop the supply of heavy water to the Nazi nuclear program was to mount a commando-style raid on the plant. This would mean sending a handful of men against a well-defended target deep in occupied territory, but the need to interrupt the supply of heavy water was all too clear, even if the means of achieving this was less so. The British turned to the only organization capable of planning and executing such a mission: the Special Operation Executive (SOE), a secret group formed in 1941 with the express purpose of sending in agents to cause mayhem in German-occupied Europe.

What resulted was one of the most remarkable raids of World War II, under the name Operation Gunnerside.