During the First World War, Bion fought in three major battles over a period of two years. He left ample writings both honest and soul searching. Travelling to The Front under raging pressure from his father, he enlisted in a state of mind, which fluctuated wildly between wanting to be a ‘hero’ and sudden fears that made him join the Tank Corps under the illusion that in a tank he would be protected. While the tank was disappointing in this respect, it put him in charge of a crew, thus giving him the first glimpse of group processes. This article charts some of Bion's experiences of war, their emotional impact on him and the transformation he underwent. The origins of some of his later thinking can be glimpsed in some of the experiences he had at this critical time in his life.