The Ambulance Mud Sleds of the Western Front
Rain and mud were constant adversaries on the Western Front. Rain flooded trenches and turned roads and fields into mud pits. Sometimes entire offensives had to be called off because the thick mud made moving men and artillery impossible.
Many parts of the western front were normally rainy, but the war years saw more rain than usual. Some of the soldiers speculated that the discharge of artillery might have seeded the clouds and brought more downpours. In any event, the peculiar conditions of trench warfare made the rains more onerous. The water filled the low lying trenches, soaking the feet of the soldiers so that they developed Trench Foot, while the constant artillery bombardments tore up the vegetation so that water collected in shell holes and turned the fields into muddy bogs. Gas and bombardments killed the vegetation which would otherwise have held back the water, turning soil into sludge.
It was hard enough to march or charge through muddy fields and up muddy escarpments when you were still fit and strong, but what happened if you were wounded? How could the stretcher bearers bring you back to a field hospital under such conditions?
The solution was to build sleds capable of being dragged over the mud. Here is a photograph of sleds (or sleighs) used for conveying the wounded through the mud of the Western Front.

These sleds were primitive but effective. They consisted of a flat wooden plank on top of two wooden runners, in much the same configuration as a sleigh used over snow. The difference was the size of the wooden skids which were wide and thick to go over the rough and muddy terrain. These sleds were harnessed to a poor horse who somehow managed to make its way over this hellish landscape.
Below is a closeup of one of the sleds showing the skids:

The rough, primitive construction of the sled is very evident in the closeup. Imagine being a wounded soldier and being dragged over rough terrain in this contraption. There were no railings to prevent the wounded man from falling off of the sleigh and no shock absorbers to give the man some protection from the bumps.
It is interesting to see that something as important as the evacuation of the wounded was left to the improvisation and ingenuity of the front line troops and medical personnel. It is obvious that these contraptions were improvised and built at the Front, without any support or supplies from headquarters, which seemed to have neglected the question of how to rescue the wounded that resulted from their strategic decisions.
This photo was taken from THE OLD FRONT LINE by John Mansfield, published in 1918.