Under the Japanese constitution — drafted by the United States after it defeated Japan in World War Two, Japan can never wage war and can never keep a military. This is why Japan does not call its military branches as "armed forces" but as "self-defence forces" (SDFs). Until Abe, Japan did not even have a defence ministry.
"When he [Abe] first became prime minister in 2006, Japan did not have a Defence Ministry. In 2007, the Defence Agency was upgraded to a Defence Ministry," noted Dhruva Jaishankar, Executive Director of Observer Research Foundation America.