In the early 20th century, a series of Sino-Japanese conflicts had raised Chinese people's concern for national unity, and the concept of a unified, undivided Chinese nation became more popular among Chinese scholars. On Jan 1, 1939, Gu Jiegang published his article "The term 'China proper' should be abolished immediately", which argued that the widely accepted area covered by "China proper" is not the actual territory of any of the Chinese dynasties. Gu further theorized that "", the Chinese and Japanese term equal to "China proper" at the time, actually originated from Japan and was translated into "China proper", hence the concept of "China proper" was developed by Japanese people, and it had become a tool to divide Chinese people, making way for the Japanese invasion of Mongolia, Manchuria, and all parts of China. Gu's article sparked a heated debate on the definition and origin of "Zhonghua minzu" (the Chinese Nation), which contributed to unifying the Chinese people in the Second Sino-Japanese war, and to an extent shaped the later established concept of Zhonghua minzu.