The battlefield placed many demands on motorcycles. It was said that the average life of a motorcycle in the battlefield was slightly over a month. Motorcycles were used by dispatch riders for communication purposes, given that radio and telephone were of limited use at the time. The condition of the roads, when there were any, were very poor. The Ministry of Munitions of the UK was reluctant to order the Enfield 3hp machines, concentrating on the sidecar combos. Other governments placed orders, including France, Belgium and Imperial Russia. Early in 1917 Germany adopted a policy of unrestricted submarine warfare (earlier in the war, submarine action was limited after the sinking of the US ship Lusitania in 1915, now the Germans were convinced the US was entering the war anyway). This wreaked havoc on supplies to the UK, in particular of fuel. Rationing was not introduced till 1918, which meant that in 1917 there were uncontrolled severe shortages of many items. Apparently the French word queue entered the English language with the meaning of "standing in line" during World War I!
The shortage of fuel led to many implications for Royal Enfield. On one hand, demand for bicycles skyrocketed (they were also used abundantly in the war). Demand for motorcycles also soared. Police departments started switching over to motorcycles, in particular the Women police force of the London Metropolitan police become the first motorcycle police personnel in the UK and the first female motorcycle corps in the world. In addition to that people started running their motorcycles on coal gas, placing balloons either in the sidecar, in trailers or on top of the bikes. Royal Enfield was never so busy, in addition to its traditional products, shells were being manufactured in Hunt End. Production reached three tons a week. The company repurchased Givry Works and expanded the Redditch factory. Here is a picture of the iconic building that says "Royal Enfield" on the roof even today, when it was built as part of the expansion of the Hewell Road plant, And it was immediately put to use as background when photographing cool motorcycles that the company was producing, as will be the case for many years,
Unencumbered by the war, people in Spain entertained themselves racing motorcycles. Look at these Royal Enfield first place finishes in the "Peña Rhin" races! (Source: "Royal Enfield, the story of the company" by Anne Bradford)