The China Marines

In Girl in the Glass, when the British officer interrogates Declan, he asks if Declan is a China Marine. Declan doesn’t know what this means, but when the U.S. government decides to smuggle the professor out of China, the China Marines are tasked with the mission.

The term "China Marines" refers to the United States Marines of the 4th Marine Regiment stationed in Shanghai, China, from 1927 to 1941. Their mission was to protect the lives, property, and businesses of Americans in Shanghai amidst political upheaval in China during the Second Sino-Japanese War (which morphed into World War II in the Pacific). 

Beyond Shanghai, US Marines were also stationed at the embassy in Beijing and the consulate in Tianjin. These Marines, known as "North China Marines", also protected American interests in the region, and are the Marines sent to escort Declan back to U.S. soil. While the China Marines' presence in China focused on military action, they also exchanged tactical knowledge, including Chinese military innovations such as guerrilla warfare and small-unit operations, elements later adapted for broader use in World War II. 

Marines in Peiping, China

Marines in Peking