Question

the war's exact start date is debated, though hostilities began as early as 1931

Answer 1

The statement you’ve made likely refers to the Second Sino-Japanese War, which is often considered to have started in 1937. However, conflicts between Japan and China, including the Japanese invasion of Manchuria, began in 1931 when Japan established control over Manchukuo. The war escalated significantly in 1937 with the Marco Polo Bridge Incident, which is commonly marked as the official start of wider hostilities. This war would eventually merge into the broader conflict of World War II in the Pacific.