Japan was not allowed to have an army after World War II?

Yes, there was no army in Japan after the war. The present Japanese Self-Defense Force was established by the United States to defend China and the Soviet Union during the Korean War.

1945 After Japan's defeat and surrender, it disbanded its army and abolished its military institutions. 1950 After the Korean War broke out, the United States instructed Japan to re-develop its military forces according to its own needs. In the same year, Japan established the "Police Reserve", which was later renamed the Guard, 1952 established the "Maritime Guard", and 1954 newly established the Air Self-Defense Force. In July, the Law on the Establishment of the Defense Agency and the Law on the Self-Defense Forces were promulgated, and the Garrison and the Coast Guard were renamed the Land Self-Defense Forces and the Maritime Self-Defense Forces respectively, and the army, navy and air force were formally established.