Hidden deep inside the American National Archives there's a highly classified document once considered as the most sensitive on Earth. In 1930 America crafted an elaborate plan for war with the "Red Empire" - the most deadly enemy. But America's enemy in this conflict was not the Soviet Union, or Japan... it was not even Nazi Germany. Plan "Red" was a code word for a massive war with Britain and all her colonies.

The plan came up during the great depression, amid expansion of evil regimes around the world, and at turbulent times when even some in America have been deluded by dark forces. This documentary will reveal how such an astonishing document came to be written and who would have won if it had been put into practice. It will show how America's greatest ally almost became their deadliest enemy.

Ward didn't a break out between Britain and America in the 1930's, but there were times when they came closer than you might imagine, as American journalist Peter Carlson was to discover. He was on a visit to the American National Archives in Washington DC when he found himself entering a strange and unsettling world.

Lying untouched for years the plan "Red" contains detailed preparations for a massive war between America and the British Empire. It shows where they would fight, what troops would be needed and how the battles would unfold. Throughout the plan the Americans refer to themselves as "blue" while the British are "reds."

The British Empire at the beginning of the 20th century was the greatest the world had ever seen, but this did cause some resentment. We now think of Britain and America as having a special relationship. After all they did fight side by side in two world wars. But at the start of the 20th century the two countries have been at each others' throats for well over a hundred years, and much of the fighting had taken place in the British dominion of Canada.