The secret of any advance through a well-defended and carefully prepared position in the Great War depended almost entirely on artillery. In spite of the popular image created by TV documentaries and military memoirs, the Great War was primarily an artillery war. Over 60 per cent of the casualties were caused by artillery, and only artillery - heavy artillery - could beat down the enemy defences, flatten the wire, stun his troops, knock out the defending batteries and let the attackers go forward.