In the First World War, it wasn't easy to get out of the trenches. Lots of different weapons were needed. One in particular... By 1915 there was a clear and undeniable stalemate across the Western Front. The weapons that the armies of the war took into battle were better for defending than attacking. Soldiers attempting to cross No Man's Land were too easily shot and shelled down by the enemy leaving them with no choice but to bunker down into the notorious trenches that have become synonymous with the war. Dan Snow begins this film by attempting to explain to his One Show colleague and some-time history sidekick Michael Douglas, how the deadlock was broken. Dan takes Michael on a quick-fire tour of how they finally came up with a solution that was as ingenious as it was simple: lots of soldiers, better weapons, perfectly co-ordinated. If there's one weapons system involved in breaking the trench stalemate that warrants particular attention it is the tank, a weapon invented by the British to deal with the very specific problem of trench warfare. It was one of the great innovations of modern warfare, a real game-changer that helped turn the course of the Great War. Dan Snow is allowed special access to the Tank Museum in Bovington, Dorset where he climbs inside, on top and all around these beasts of the battlefield in order to explain not only how they changed the nature of warfare but how they rapidly evolved from the 1915 prototype Little Willie, the first tank, through to the iconic Mark IV, the comparatively speedy Mark A Whippet tank and the huge International, an Anglo-American designed tank that showed how far this revolutionary weapon had changed within just a few years of its invention.