Kammala wannan magana: Yankin bincike na uku da Hasegawa ya gudanar shine tarihin kasa da kasa wanda ya shafi Tarayyar Soviet, Amurka, da Japan a kawo karshen yakin Pacific. Yayin da Amirka ta jefa bama-baman nukiliya a Hiroshima da Nagasaki a watan Agusta na shekara ta 1945, mutane miliyan ɗaya da ɗari shida
Sojojin Soviet sun kaddamar da harin ba zato ba tsammani a kan sojojin Japan da ke mamaye gabashin Asiya. Hasegawa ya wallafa littafi, "Racing the Enemy: Stalin, Truman, da kuma Bayar da Japan" (2005). Da yake kalubalantar ra'ayin da aka yarda da shi a ko'ina cewa bama-bamai na nukiliya a Hiroshima da Nagasaki sune mafi mahimmancin mahimmanci a cikin shawarar Japan don mika wuya da kawo karshen Pacific, Hasegawa ya gabatar da ra'ayin cewa shigar da Soviet cikin yaƙin, ta hanyar warware Yarjejeniyar Neutrality, ta taka muhimmiyar rawa fiye da bama-bamai na nukiliya a cikin shawarar Japan don mika wuya. Wannan ra'ayi ya bambanta da masu sukar farko na fashewar bam, kamar Gar Alperovitz, wanda ya yi jayayya cewa babban burin Shugaba Harry S. Truman na Amurka shi ne nuna ikon sojojin Amurka a matsayin abin hanawa ga burin shugaban Soviet Joseph Stalin. In ji ɗan tarihi na Australiya Geoffrey Jukes, "[Hasegawa] ya nuna sarai cewa sanarwar yaƙi na Soviet ne, ba bama-bamai ba, da ya tilasta wa Jafananci su miƙa wuya babu gaira babu dalili". An soki ra'ayinsa. An ba da tattaunawar da ta fi dacewa da wannan littafin a cikin tattaunawar zagaye na H-Diplo tare da Gar Alperovitz, Michael Gordin, David Holloway, Richard Frank, da Baron Bernstein. James Maddox, Farfesa na Tarihi Emeritus a Jami'ar Jihar Pennsylvania, kuma marubucin "Makamai don Nasara: Hukuncin Hiroshima Shekaru Hamsin Daga baya", yana ɗaya daga cikin masu sukar littafin.