The Sino-American Cooperative (SACO)

In Girl in the Glass, Bruce explains to Declan why the Chinese are willing to let the Clypeate keep the Epistolith found inside the Longmen Grottoes. Bruce explains:

“Our government is working out a deal, a Sino-American cooperative, to help China win back their country. In exchange for sharing our intelligence gathering skills, we get the Epistolith after the war.”

The term "Sino-American Cooperative" refers to the Sino-American Cooperative Organization (SACO), an intelligence and military collaboration formed between the United States and Nationalist China during World War II, primarily aimed at fighting the Japanese invasion. 

Established through the 1942 SACO Treaty, SACO involved US forces working alongside Chinese Nationalist troops, sharing intelligence and training jointly. SACO units established communication, aircraft monitoring, and intelligence stations across China, including along the coast behind Japanese lines, ultimately helping defeat Japan and liberate China.