Hasegawa was born as the son of a samurai fencing master in the Iwakuni sub-fief of Chōshū (present-day Yamaguchi Prefecture), Hasegawa served under the Chōshū forces during the Boshin War from January until March 1868 during the Meiji Restoration which overthrew the Tokugawa shogunate.

Later, as a major, he was given command of a regiment during the Satsuma Rebellion, and saw action at the relief of Kumamoto Castle on 14 April 1877.

During the First Sino-Japanese War, Hasegawa won distinction for valor on behalf of his 12th Infantry Brigade at the Battle of Pyongyang on 15 September 1894 and in skirmishes around Haicheng from December 1894 until January 1895.

During the Russo-Japanese War, Hasegawa was assigned to the First Army under General Kuroki Tamemoto as commander of the Imperial Guards Division in the spring of 1904.

From October 1916, he served as the second Japanese Governor-General of Korea, and was later criticized for his military approach to the Samil Independence Movement.