Cypher Evolution is the second part in the three-volume series recounting the history of I Battery (Bull's Troop) R.H.A. This book covers the two world wars and the period afterwards, up to 1962 when the battery became part of the airborne artillery. It also considers the developments that took place in the artillery, both strategically and physically, through the trenches of World War I, the challenges of post-war Britain, and the move to the mechanised artillery of World War II that helped to shape the face of modern warfare.