What event showed the aggression of the Japanese military?

The aggression of the Japanese military was prominently showcased during the Nanjing Massacre in 1937, when Japanese troops captured the Chinese city of Nanjing and committed widespread atrocities, including mass executions, sexual violence, and looting. This brutal episode resulted in the deaths of an estimated 200,000 to 300,000 individuals and exemplified Japan's expansionist policies and militaristic approach during the Second Sino-Japanese War. The event highlighted the extreme measures taken by the Japanese military in their efforts to dominate Asia.