Genfer Abrüstungskonferenz
Hasegawa was promoted to rear admiral on 1 December 1927 and appointed commander of the Yokosuka Naval District. He was appointed commander of the Third Torpedo Squadron on 1 September 1929 and appointed commander of the Submarine Squadron on 30 November. The following year, he was appointed head of naval policy in the Navy Ministry, and appointed commander of the Kure Naval Arsenal on 1 December 1931. Re-appointed to the Naval General Staff in October 1932, Hasegawa attended the World Disarmament Conference in Geneva from April to October 1933. He was promoted to vice-admiral on 1 December 1933 and became Vice-Minister of the Navy in May 1934.