In the event of a German invasion, Britain would have looked to make a coastal landing as costly and chaotic as possible, with defensive action starting before the Germans even reached the shore. In this episode we explore the mine control towers, beach defenses, and strategic forts along Britain's south coast that would form the first line of defense.

The protection of its cities was a vital part of Britain’s defense plan. In this episode we explore the structures built into the natural hill barriers surrounding London, the air raid shelters built to protect the capital's 8 million inhabitants during the Blitz, and the incredible "starfish" sites constructed to confuse Nazi bombers.

If Britain’s coastline defenses had failed, the battle would move to the fields and countryside. In this episode we explore the intricate network of defenses known as the Stop Lines – a series of interlinking barriers that the British would fall back to and use to halt or slow down the German advance.

After Dunkirk, Britain needed to buy time to build up its defenses. In this episode we explore the integrated network of structures and airfields comprising the "best air defense system in the world" that would enable the RAF to win the Battle of Britain.

While Britain hoped its sea, land, and air defenses would hold, plans had to be made should a German invasion prove unstoppable. In this episode we explore the fortifications at Reigate Hill which would act as a resistance HQ if London fell, and the network of secret structures to be used by the auxiliary units trained for a clandestine fight under Nazi occupation. We also examine the plans to relocate the Royal family and Government, and visit the remarkable underground locations prepared to keep the BBC broadcasting, and protect Britain’s art treasures.

In 1941 the threat of invasion still loomed, but Britain was now growing stronger, and rearmament was gathering pace. In this episode we explore Britain’s shadow factories, hidden from German bombs, including the aircraft engine factories buried underground, and the Avro Factory used to manufacture the Lancaster bomber which was cleverly disguised as a working farm.

By 1942 the Americans had entered the European conflict, and the tide was starting to turn. In this episode we explore the extensive air and naval structures used by Britain and her Allies in preparation for the fight back against the Nazis.

In 1944 the greatest invasion in human history was being prepared across southern Britain. In this episode we explore the buildings and incredible structures used in the planning and execution of the D-Day landings - the largest and most complex amphibious operation in military history.