[1] Born in Matsumoto, Nagano, Iwai left school in 1937 and began working as a locomotive hand on the Japan National Railways.
[5] Iwai also helped oversee Sōhyō's militant role in the 1960 Anpo protests against the U.S.-Japan Security Treaty and the 1960 Mitsui Miike Coal Mine Strike.
However, both the Anpo and Miike struggles came to be viewed as defeats for the labor movement, as the Anpo protests failed to stop passage of a revised security treaty, and the Miike miners' union was broken when Mitsui corporation succeeded in hiving off a more pliable "second union" and reopening the mine.
[6] After these perceived failures, Iwai and Ōta sought to further moderate Sōhyō's renowned militancy, shying away from political protests and focusing more on bread-and-butter issues such as securing piecemeal workplace improvements and wage increases, negotiated amicably with employers in advance of the annual shuntō spring wage offensive.
When Sōhyō's public-sector unions threatened to go on strike in 1964, in defiance of a law banning public-sector workers from striking, Ōta and Iwai met face-to-face with Prime Minister of Japan Ikeda Hayato, and successfully negotiated an annual increase in public sector wages that would match pay in the private sector, in exchange for a promise to further reduce labor militancy.