Hitler transformed his Alpine retreat in Bavaria into a fortified fiefdom, home to 2,000 SS troops and protected by a high level security system.

It’s June 1940 and the Nazis have taken the Channel Islands, where Hitler orders some of the most fortified structures in the Third Reich.

Hitler planned a submarine to outperform all others. The Type 21 was the world's most advanced submarine: Hitler's sea-faring super weapon.

In the 1930s the Japanese begin designing the Yamato, the world's most powerful battleship, 30 per cent larger than anything their enemies have.

In 1945 Japanese generals construct a network of defences and tunnels on Okinawa, creating a devastating killing ground for American troops.