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Japanese invasion of China
On July 7, 1937 a scuffle between Chinese and Japanese troops occurred near Peiping in North China. This scuffle was named the Marco Polo Bridge Incident. This event happened because Japan wanted the natural resources in China so they invaded Manchuria to get closer to China. This event led to the second Sino-Japanese War. Japan quickly seized many of China's main ports and industrial centers.
http://www.history.co.uk/study-topics/history-of-ww2/sino-japanese-war