Osterhagen Project

The Osterhagen Project was a defence weapon consisting of a series of nuclear warheads placed at strategic points beneath the Earth's crust and a last resort that would sacrifice the planet in the hope of taking its enemies with it.

Overview
The Osterhagen Project was a planetary self-destruct system. It was meant to be used only if humanity were suffering unbearably, with no hope of help ever coming. The Osterhagen system was a chain of twenty-five nuclear warheads placed in strategic points beneath the Earth's crust. If the key was used, the system would be activated and the Earth would be ripped apart.

The Osterhagen keys were distributed among various high-ranking UNIT personnel across the globe. There was at least one key for each of the five stations known to be operational. (TV: Journey's End)

In 2009, General Sanchez was in possession of an Osterhagen key. During the Dalek invasion of Earth, Sanchez authorised Martha Jones to use it if she failed to contact the Tenth Doctor. (TV: The Stolen Earth) Two other keys were given to UNIT soldiers in Africa and Asia. (TV: Journey's End)

Osterhagen stations
There were at least five Osterhagen Stations located across the world but only three needed to be manned for the system to work. Osterhagen Station 1 was located sixty miles outside of Nuremberg, Osterhagen Station 4 was located in Liberia and Osterhagen Station 5 was located in China. Another station was located in Argentina. (TV: Journey's End)

Threatened use
After Earth fell to the Daleks, in 2009, General Sanchez of UNIT gave a key to Martha Jones, along with the prototype of Project Indigo, to escape. However, former Prime Minister Harriet Jones told Martha not to use the Osterhagen key under any circumstances. (TV: The Stolen Earth)

Believing the Dalek invasion unstoppable, Martha made her way to Germany. She activated the station there and contacted two UNIT soldiers, one Anna Zhou of China, another a Liberian who refused to give his name. UNIT protocol stated that the keys should be used immediately upon the activation of any three stations, but Martha delayed their use to offer the Daleks a chance to surrender. Discovering that the Doctor had been captured, Martha attempted to blackmail the Daleks into releasing him, but the Daleks transmatted her to the Crucible before she could insert the key, disarming the system.

Martha claimed that the Earth would be ripped apart, making the reality bomb useless, since it used Earth as part of its mechanism. After the War in the Medusa Cascade, the Doctor asked Martha to persuade UNIT to dismantle the "Osterhagen Project" altogether, to prevent it being abused in the future. (TV: Journey's End)

Principle
During the Second Dalek War, the planet Auros was once found burning by the Doctor and the crew of the Wayfarer. Her captain, Jon Bowman, described the devastation as "the Osterhagen Principle". The planet had been destroyed to stop it from falling to the Daleks as their fleet drew nearer. Nevertheless, the Daleks anticipated this move and the Auros evacuation fleet was driven into a trap devised by Dalek X. (PROSE: Prisoner of the Daleks)

Other information
Though the Doctor had asked Martha to see to the dismantling of the Osterhagen Project, (TV: Journey's End) its use on Auros during the 26th century showed that some trace of information regarding the Osterhagen Project lived on, either through classified files or word of mouth passed down by high-ranking officials. (PROSE: Prisoner of the Daleks)

The German woman who provided food for UNIT forces at Osterhagen Station 1 implied that the Project had been around since her visit as a youth to London. (TV: Journey's End)

Jack Harkness of Torchwood Three was able to learn the details of another top-secret UNIT initiative, Project Indigo, but he had no knowledge of the key.

However, several people outside UNIT knew of the key, such as former Prime Minister Harriet Jones. (TV: The Stolen Earth)

The Doctor surmised the Osterhagen Project and key were invented and named after someone called "Osterhagen". (TV: Journey's End)

Behind the scenes

 * "Osterhagen" is the name of an actual German village.
 * In the original script, the Osterhagen key was called the "Stattenheim" key. (The Writer's Tale)