On 24 April 1941, 21-year-old Frank Joseph Gill was in the port of Piraeus, unimaginably far from his home in Liverpool, England. His sweat-stained uniform showed that he was a Lance-Corporal in the Royal Engineers. He was part of a band of servicemen from the UK, Australia, and New Zealand who had been ordered to evacuate from Greece, in anticipation of the imminent arrival of German troops. Along with hundreds of civilians and other servicemen, he boarded the yacht SS Hella

It is impossible not to be charmed by Athens. At night, bouzouki music wells up from dark basements; tables spill out of ouzeris, around...