Which region of the world can make the earliest claim that WWII began in their country?

The region of the world that can make the earliest claim that World War II (WWII) began in their country is East Asia, specifically China. The Second Sino-Japanese War, which began on July 7, 1937, when the Japanese Empire and China’s Nationalist government led by Chiang Kai-shek clashed at the Marco Polo Bridge near Beijing, is often considered by many historians as the start of WWII in Asia. Although World War II is officially recognized to have begun on September 1, 1939, when Germany invaded Poland, the conflict in Asia that would eventually merge with the global conflict had already been underway for two years.

The Second Sino-Japanese War started after a series of incidents and escalating tensions between Japan and China. Japan, pursuing a policy of imperial expansion, sought to control more territories in Asia and viewed China as a key part of its plans for a greater East Asia co-prosperity sphere. The Marco Polo Bridge Incident was the catalyst for full-scale war, and over the next eight years, the conflict merged with the wider global war. The invasion of Poland by Nazi Germany in 1939 marked the beginning of the war in Europe, and after Japan's attack on Pearl Harbor on December 7, 1941, the U.S. and its allies declared war on Japan, fully merging the Asian and European theaters of war into one global conflict known as World War II.

Thus, while the official date marking the beginning of WWII is associated with the European theater, if we consider the broader scope of military conflicts that contributed to the war, China’s experience with Japanese aggression marks the earliest phase of what would become a global conflict.