Hata's first published history book was "Nicchū Sensōshi" ("A History of the Second Sino-Japanese War"), released in 1961, which he began researching while completing his bachelor's degree at the University of Tokyo. The work was well-received, described by Chalmers Johnson as "the most thorough study of Japanese policies in China during the 1930s" and by James T.C. Liu as "a welcome and pioneering contribution". Fifty years after its publication Edward Drea and Tobe Ryoichi called it "a classic account" of the war. Hata's second book, the 1962 work "Gun fashizumu undō shi" ("A History of the Military Fascist Movement"), was promoted by the historian Shuhei Domon as "a first-rate narrative interpretation based on extensive use of documentary evidence."