It was 1948 that United Nations founded the first PKO. But it's not so long since Japan participated in PKO.

Since joining the United Nations in 1956, Japan has actively participated in the U.N. activities as one of the important factors of its diplomatic policy in other respects than man power.
After the Gulf Crisis in 1991, finally the argument that Japan should play a more positive role for the world peace, by providing not only funds or goods but also man power became popular. In June,1992, International Peace Cooperation Law was established in Japan, that permits dispatch of people for the sake of cooperation for the world peace. It permitted the Japan Self-Defense Forces to participate in, and also opened the door to practical cooperation for the U.N. peace-keeping activities, and international rescue activities in a humanitarian way. Japan has sent over 2,000 persons and they have greatly contributed to the world peace and security since then.