In addition to the dead and wounded, government leaders feared mass psychological trauma from aerial attack and a resulting collapse of civil society. A committee of psychiatrists reported to the government in 1938 that there would be three times as many mental as physical casualties from aerial bombing, implying three to four million psychiatric patients. Winston Churchill told Parliament in 1934, "We must expect that, under the pressure of continuous attack upon London, at least three or four million people would be driven out into the open country around the metropolis." Panicked reactions during the Munich crisis, such as the migration by 150,000 to Wales, contributed to fear of societal chaos.
Psychiatrists believe in 1938  that mental trauma could reach how many millions?
three to four