As German planes began bombing London in 1939, the British government had no doubts societal breakdown would ensue. Civilians were not ready for the trauma and horrors to come:

How would they cope with a complete change to life as they knew it? How would they respond to the nightly threat of injury or death? Would they riot, loot, experience mass-scale psychotic breaks, go on murderous rampages, or lapse into total inertia as a result of exposure to German bombing campaigns? ... Some in the government feared three times as many psychiatric casualties as physical ones.

Known as the Blitz, the bombing campaign killed over 60,000 civilians. But to the surprise of government officials, the expected breakdowns never materialized:

In fact, the Blitz achieved the opposite of what the attackers intended: the British people proved more resilient than anyone predicted. Morale remained high, and there didn’t appear to be an increase in mental health problems. ... Some people with longstanding mental health issues found themselves feeling better.

People in British cities came together like never before to organize themselves at the community level. The sense of collective purpose this created led many to experience better mental health than they’d ever had. One indicator of this is that children who remained with their parents fared better than those evacuated to the safety of the countryside. The stress of the aerial bombardment didn’t override the benefits of staying in their city communities.