On his return to Japan, he was posted to the Imperial Japanese Army General Staff, and headed a Russian studies department.

From the middle of 1930, Hashimoto became increasingly involved in right-wing politics within the military, with active participation in various attempts at a coup d'état.

Supporters of Fumimaro Konoe's "Right-Socialist" revolution (populist ideas, which were rooted in the poorest farmers, fishermen, and industrial workers) opposed the "right-wing" militarists represented by Senjuro Hayashi in the same "revolutionary grouping".

Throughout the war, the Yokusan Sonendan (Imperial Rule Assistance Young Men's Corps), under his leadership, had the mission of guiding the nationalist and militarist indoctrination of the youth.

Hashimoto was the senior Japanese officer in the region, and a few days after the sinking, he was quoted in US newspapers as saying "I had orders to fire."

Hashimoto greatly supported aggressive policies during the Second Sino-Japanese War and the Tripartite Pact with Nazi Germany and Fascist Italy in 1940, along with the other military extremists of the Imperial Japanese Army.