A wedding ceremony in Liverpool in April 1943 depicts an unknown Chinese merchant seaman (front, third from left) and his new British wife.

Forcible repatriation

According to Han's research, about 6,000 Chinese sailors married or cohabited with local women, fathering more than 1,300 children. However, in September 1945, the British government began to forcibly repatriate the Chinese sailors. Many were denied the opportunity to say goodbye to their families because they were detained on the street and sent directly to the ships that transported them back to China. The men's sudden departure had a devastating effect on those left behind.

Yvonne Foley was born in February 1946, a few months after her father, who hailed from Shanghai, was forced to return to China. Foley's mother was too ill to accompany her husband, so she stayed in the UK.

"Back then, we didn't ask questions. As for my mum, she always thought she'd been abandoned, so there was that hurt that made it difficult," Foley said, in an interview with the BBC last year.

For the past decade, she has acted as the leader of a group for men and women whose fathers were repatriated, collecting any snippets of information that will help to provide a clearer picture of what happened to the men.

On the group's website, Liverpool and its Chinese Seamen, they wrote: "Some of us did not know we had any Chinese blood until we were teenagers or even adults. We knew we looked different to others around us, but we never knew why."

The prevailing conditions of the time meant that although many families tried to maintain contact, few managed to do so.

According to Han, a small number of the children traveled to China in the 1980s and '90s and found their fathers. However, as many of the children are now in their 70s and 80s, and most of the fathers have died, they are finding it increasingly difficult to trace their roots.

Han is currently helping the China Maritime Museum in Shanghai to organize an exhibition about the lives of Chinese seamen in wartime Europe. It will open before June 25, the International Maritime Organization's "Day of the Seafarer".

"The Chinese sailors played an important role in the victory in the war," he said. "They should not be forgotten."