Cyril Falls, The Art of War from The Age of Napoleon to The Present Day (1961)
In the First World War ‘cellar life’ had been a feature of the adversities of Paris, which actually came under the fire of specially built long-range guns in 1918, as well as aircraft bombing. In the East End of London air raids cause a tendency to panic in the latter part of 1917, and, whether there was a raid or not, some 300,000 people crowded each night into the underground railway stations and slept on the platforms … There was little organized civil defence beyond the reduction of lights.
The Germans, who were far ahead of any rival in the science of lighter-than-air construction, refused to accept the general belief that the future lay entirely with the heavier-than-air. Their Zeppelins … were employed chiefly in night attacks on England. On one occasion a single airship did a million pounds worth of damage in a raid, but on the whole their success was mainly moral and measured in terms of absenteeism in factories and sensational drops in production of warlike material.
Early in the war the German Armies owed much in their victories in Poland, Belgium, and France to their dive-bombers. These aircraft acted in close support to the armour and infantry … They often put hostile artillery out of action, but generally by driving the detachments from their guns. The successes were won for the most part by moral rather than material effect. To troops unused to them, especially the French division of low categories, they proved extremely unsettling.