By 1936 it was clear to defence strategists that, in the event of a war, the air would be a new theatre of war. Aerial bombing of cities and civilian targets was to be expected, with the development of aircraft over the previous twenty years making it both possible and likely. In Britain, the Air Ministry calculated that aerial bombing could cause up to 200,000 casualties per week. It was during this period that the British government considered relocating key governmental department offices out of London to somewhere in the countryside, therefore protecting them from any potential bombing raids. In the end, the vast relocation of offices did not happen, however it was agreed that an emergency government building should be built, somewhere where the cabinet could meet in relative safety, should London be under attack from the air.
The site chosen for these underground offices was the New Public Offices, a building roughly half way between 10 Downing Street and Westminster Palace, and right in the heart of Whitehall. Construction on the reinforced, bomb-proof basement began in 1938, with the project managed by Sir Hastings Ismay and Sir Leslie Hollis. The basement was fitted out with military broadcasting and communications equipment, and was ventilated to allow for around the clock habitation.
The war rooms opened on the 27th of August, 1939, just six days before Germany invaded Poland and eight days before Britain declared war on Germany. The world was at war, and it wasn't long before London was the target of aerial bombing, just as the defence chiefs had predicted it would be. Throughout the Blitz, as the bombs of the Luftwaffe rained down on London, Churchill and his government ministers met at the war rooms and discussed war tactics. It was the place, Churchill said in May of 1940, 'from which I will direct the war'.
For the entirety of the war, cabinet meetings were held at the war rooms, 115 of them in total. Churchill was not exaggerating when he said, in May of 1940, that the rooms would be the place 'from which I will direct the war'. The bunker included a Transatlantic Telephone Room, and it was from there where Churchill had regular telephone meetings with the American President Roosevelt.
Following the war, due to the historical importance of the cabinet war rooms, there were calls for the rooms to be preserved and converted into a museum. In 1974 the Imperial War Museum acquired the war rooms, and finally in 1984 – 39 years after the end of the Second World War – the war rooms were opened up to the public. Today known as the 'Churchill War Rooms' they are visited by over 300,000 people a year. 72 years after the surrender of Japan and the end of World War Two, the map room, cabinet meeting room, offices and staff bedrooms are all preserved exactly as they were when they were abandoned on that fateful August of 1945.