It seemed like a good idea at the time

“After the seizure of Mukden the Japanese Army, regardless of divided councils at home, pushed ahead to attack Chinchow, Chang Hsueh-liang’s provincial capital just north of the Great Wall. They captured the city in January 1932, driving the Young Marshal out of Manchuria. The ‘independence’ of the new state of ‘Manchukuo’ was proclaimed in February and Henry Pu-yi, last relic of the Manchu dynasty, was installed as Regent in March. The Japanese Government, under the necessity of accommodating to the stranglehold of the Army and Navy ministers, was dragged forward by faits accomplis and by the blackmail of violent nationalism. Because it was anxious not to give the League of Nations or the signatories of the Nine-Power Treaty a reason to declare that a state of war existed between Japan and China, Tokyo attempted to legalize each forward move on the mainland as ‘self-defense’ and ‘self-determination’ by the people of Manchuria.” – Barbara Tuchman, Stillwell and the American Experience in China