土肥原賢二
A native of Kumamoto Prefecture, his original surname was Mori, but he was adopted into the Sonobe family as a child. After attending military preparatory schools in Kumamoto and Tokyo, Sonobe graduated from the 16th class of the Imperial Japanese Army Academy in 1904. HIs classmates included Yasuji Okamura, Kenji Doihara, Rikichi Andō and Seishiro Itagaki. After serving as a junior officer with the IJA 23rd Infantry Regiment, he graduated from the 25th class of the Army Staff College and was assigned to the IJA 23rd Infantry Regiment.