Epidemics took many lives. While many lives were lost to serious diseases from food and water contaminated by sewage, minor ailments took their toll. Because of the cramped conditions, measles spread especially well.

Many people who were recovered by stretcher-bearers, died because battle medicine was still in its early stages. The huge tented hospitals where people were treated had to be run on a large scale, so not much individual attention could be given. There were no painkillers or antibiotics, X-rays were very rare, and needles were not sterilised. Many wounds turned septic and gangrenous – leading to amputations and death.

When the Americans joined the war, they brought much needed knowledge of blood transfusions. Earlier in the war the British had experimented with these, but were unsuccessful because the blood types were not yet understood.

One of the worst aspects for soldiers in the trenches was mud. Very wet weather and the destruction of drainage systems quickly led to a quagmire. The problem of mud was most acute at Passchendaele, or as it became know, "the battle in the mud". Brushwood tracks were laid down to show the safe path. But the thick slime, which reached men’s knees, consumed all who strayed off the safe path. If a man became stuck fast, he often begged his friends to shoot him, rather than die of suffocation. The problem the mud posed was best demonstrated by those who spent most time in it – the stretcher-bearers. Normally, two men would be sufficient to carry a stretcher : at Passchendaele it required sixteen (Fig.17).

The British Commander-in-chief, Sir Douglas Haig, admitted that attack was suicidal in such conditions ("The ground is like a bog"). A German commander echoed this by saying: "The mud is our most effective ally." Unfortunately, at Passchendaele, and other great battles, mud was nobody’s friend.