Pre-War Japanese Aggression refers to the series of militaristic and expansionist policies and actions taken by Japan in the 1930s, leading up to its involvement in World War II. This period is marked by Japan's invasion of Manchuria in 1931 and its subsequent military campaigns in China, which demonstrated a clear intent to establish dominance in East Asia. These aggressive actions not only contributed to regional instability but also set the stage for Japan's broader ambitions that ultimately led to conflicts with Western powers.