It was Iwasawa's intention to return to Japan in 1952 after his visit to the Institute for Advanced Study but when he received the offer of a post of assistant professor at the Massachusetts Institute of Technology he decided to accept it. Coates, in [), describes the fundamental ideas which Iwasawa introduced that have had such a fundamental impact on the development of mathematics in the second half of the 20th century. Iwasawa introduced:
Ito ay Iwasawa ang balak na bumalik sa bansang Hapon sa 1952 matapos ang kanyang pagbisita sa Institute for Advanced Study ngunit kapag natanggap niya ang alok ng isang post ng mga assistant professor sa Massachusetts Institute of Technology siya ay nagpasya na tanggapin ito. Coates, sa [), na naglalarawan ng pangunahing ideya na Iwasawa ipinakilala na may tulad na isang pangunahing epekto sa pag-unlad ng matematika sa ikalawang kalahati ng ika-20 siglo. Iwasawa nagpasimula ng: