From 1873, all Imperial Japanese males were required to serve three years of active military duty and four years in the reserves.
Emulation of Western imperialism and security concerns resulted in the Russo-Japanese War of 1905.
By the 1930s, assuming the role of the big brother who promoted co-prosperity for Asia, Japan increasingly faced down provocations by Western powers.
Mounting economic concerns in the 1930s further drove Japan’s expansionism in East Asia.