How to keep an army fed and housed. Disease has killed more men than any other enemy. Saul sees how amazingly similar today’s Camp Bastion in Afghanistan is to Roman military bases in England, and discovers how the introduction of canned food changed everything. From dysentery in medieval Agincourt to the hideous tropical illnesses of the 19th century, Saul comes face to face with the physical and psychological devastation that disease can wreak.