Why did japan call war on china in 1937?

Japan declared war on China in 1937 primarily due to its expansionist ambitions in East Asia and the desire to secure resources and territory. Tensions had been escalating since the 1931 invasion of Manchuria, and incidents like the Marco Polo Bridge Incident in July 1937 provided a pretext for full-scale conflict. Japan aimed to establish a greater East Asian co-prosperity sphere, viewing control over China as essential to its imperial strategy. The war ultimately led to significant devastation and loss of life, contributing to the broader context of World War II.