Chinese, Japanese, Indians and other refugees from Germany and Austria lived in Hongkew. Shanghai at that time witnessed 1,000 monthly refugee arrivals, and Hongkew residents faced dire conditions since the start of the war in China in 1937, according to the Shanghai Jewish Museum.

In less than 1 square mile, the ghetto was home to some 10,000 native Chinese residents living side by side with thousands of Jewish refugees, the museum said.

The Chaim family lived next to a Chinese family. Kracko's mother would send cookies to the Chinese lady who lived downstairs, and the Chinese lady, even though she could not communicate with them, would give her some noodles in return.

Lindenstraus also had a Chinese family as neighbors in Hongkew. The Chinese family lived downstairs with their children and chickens, while Lindenstraus' family lived upstairs.

They were friendly with each other, but they did not understand each other's languages. Therefore, they communicated using pidgin English, a combination of English, German and Chinese words, Lindenstraus said.

"Believe it or not, the Chinese (who lived in Hongkew) were (treated) worse than we were," Lindenstraus said. "The Japanese treated them terribly. The Chinese had to bow (when they saw the Japanese). We didn't have to bow. But I've seen it. The Chinese didn't bow deep enough, boom, they were killed. It's terrible."

One school day, Lindenstraus' class went to a public swimming pool outside of the ghetto. It was a hot, muggy day, and he and Kirchner spent hours in the pool. When it was time to leave, the two boys didn't hear the signal and were left behind, Lindenstraus said.

They were picked up by a Japanese Army truck.

"We were very scared," Lindenstraus said. When they finally arrived home, they found that Lindenstraus' stepmother was so worried that she blamed everything on Kirchner and his mother, and the two mothers had a big fight.

Sheltered in Shanghai, Lindenstraus, along with many other Jewish refugees, did not know what had happened in Europe and the Holocaust, in which 6 million Jews across Europe were murdered, until Japan surrendered in 1945.