What personal experience does Hersey utilize in writing the novel, The Call?

A child of missionary parents, John Hersey spent the first ten years of his life in Tientsin, China. During this time he acquired a knowledge of conversational Mandarin that he never lost. He had spoken the language before he learned English. He also never lost his love and admiration of the Chinese people. At the age of seventyone, he wrote The Call, a novel whose hero is a young missionary stationed in China in the early through mid-1900s.