Dr. Sam Willis investigates two of the war's most hi-tech and deadly elements. In part one he looks at the reality of being attacked by one of the German navy's highly effective submarine fleet: a U-Boat. At first, the British Admiralty underestimated the offensive threat posed by the German U-Boats but they very quickly realized that the Royal Navy was facing one of the greatest threats in its history. Yet it wasn't just the Navy that had to contend with the lurking threat beneath the waves. In 1915, the German Admiralty began to pursue its controversial policy of unrestricted warfare against all enemy shipping. In part two Sam travels to Salisbury Plain where the Royal Engineers are training with deadly high explosives. The Royal Engineers have an illustrious history and reputation within the British Army for coming up with clever innovations to solve the myriad problems that occur in any conflict. Repairing bridges, digging tunnels and building roads are all vital elements of their work. They are also very good at blowing things up. One of the great menaces of the Western Front during WW1 was barbed wire and the Engineers were charged with finding an effective solution. Sam gets as close as anybody would want to be as today’s Engineers detonate a range of sophisticated and devastating blasts, including the Bangalore Torpedo… based on the same design that was used 100 years earlier to combat the barbed wire