The First World War

The evolving naval and intelligence war during the First World War, which saw enemy submarines turn the North Sea into a no-go area. The British responded with a blockade of Europe, and America threw its full support behind the Allies after a deciphered telegram revealed Germany was urging Mexico to attack the United States.

The wartime employment of spies, blockades and intelligence-gathering, which proved just as important as battleships at a time when governments faced continuing risks of mutiny, low morale, strikes and civil disobedience.

Agents were sent to create unrest among the enemy, including the British-sponsored Arab Revolt led by Lawrence of Arabia, and Germany's support of Irish independence by supplying arms for the Easter Rising.

The penultimate episode explores Germany's bid to end the conflict by launching Kaiserschlacht, a massive offensive on the Western Front, masterminded by General Erich Ludendorff. Within days the British Fifth Army was in retreat, Paris was under shellfire and defeat seemed inevitable. However, the plan ran out of steam as supplies and strategic options dried up and German troops became war-weary, hungry and demoralised.

The last episode charting the final months of the First World War, which saw the Allies learning to pull together using a coordinated command structure and the mass-production of hi-tech weapons, while the Germans remained on French soil, believing victory to be inevitable.

The dramatic Allied victory at Amiens led to victory in just 100 days - and the signing of a bitterly-resented peace, while other nations stumbled towards their own ceasefire agreements.