When World War II began, Adam was working on designs for air-raid shelters and illustrated books on air-raid protection and gas masks. As German citizens, the Adam family could have been interned as enemy aliens, but in October 1940 Adam was able to join the Pioneer Corps, a support unit of the British Army open to citizens of Axis countries resident in the UK and other Commonwealth countries, provided they were not considered a risk to security. Adam was seconded to design bomb shelters.