Sun Yaxing, the twenty-seven-year-old bachelor who organized the bombings of July 7,1938, was the son of a traveling salesman from Jinjiang. He had five years of primary school and three years of private tutoring before coming to Shanghai at the age of fourteen to live with an aunt at the corner of Bubbling Well and Hardoon Roads. After another six months of primary school, he studied for a year at a Hankou middle school and then came back to Shanghai to learn the watch trade in the shop of one of his father's friends. During his four years of apprenticeship as a jeweler he also took evening classes in a private night school. By the time his training was completed early in 1931, he was ready to open his own jewelry store, the Xingxiang (Prosperity and Good Fortune), on rue Palikao in the French Concession. A few months later the Manchurian Railway incident occurred, and Sun promptly closed his shop doors and joined the Shanghai Citizens Volunteer Corps “with a view to serving my country in a more beneficial manner.”

The Shanghai Citizens Volunteer Corps, run out of an office over a Fuzhou Road silk shop by a lawyer named Wang Bingnan, had 500 members when Sun Yaxing joined up. On January 28, 1932, after some military drills on the public recreation ground of Nandao, 300 of these young men agreed to participate in the conflict. Sun was named a section chief by Wang Binnan, who led the group to Baoshan where they were drafted into the Chinese military and attached to the 19th Route Army.