Watanabe was the second son of a former
samurai retainer of the
Kishiwada Domain who became an elementary school teacher after the
Meiji restoration. Watanabe attended military preparatory schools in Osaka and was a graduate of the 21st class of the
Imperial Japanese Army Academy in 1909, specializing in artillery. He graduated from the 31st class of the
Army Staff College in 1919. After graduation, he held various staff positions, and from 1928 was an instructor of the Army Field Artillery School. In 1928, he was promoted to the honorific title of Senior Sixth
Court Rank. He was on the staff of the
Hiroshima Port Fortress, the
Hōyo Strait Fortress, and commanded the
Guards Field Artillery Battalion, rising to the position of
Chief of Staff of the
IJA 14th Division in 1933, overseeing its withdrawal from
Manchukuo back to Japan. Watanabe was promoted to
major general in 1937 and was made Chief of Staff of the
Central District Army in Japan. From 1938 to 1940 the head of the Army Armaments Factory. He was promoted to
lieutenant general in 1939. After a brief stint at the Army Aviation Technology Research Institute, he was given a field command as the commander of the newly formed
IJA 56th Division from August 1940. Although initially the 56th division was slated as reinforcements for the
Japanese invasion of Malaya, the rapid cessation of British resistance resulted in division been attached to
IJA 25th Army and sent to
Burma in March 1942, landing in
Rangoon and participating in the
Battle of Toungoo. The 56th Division linked with the
IJA 55th Division in
Toungoo on 28 March 1942. Its reconnaissance elements forced the Chinese to evacuate the city opening the way to the east. Later the 56th Division flanked the Allied line to the east, by advancing through the mountains to the Salween River in the
Karenni States. The Division defeated the Chinese 6th Corps in the
Karen Hills area battles of
Mawchi on 13 April 1942,
Bawlake,
Taunggyi and
Loikaw on 20 April 1940, and forced their retreat eastward to
Yunnan. Advancing north through the
Shan States the 56th Division defeated elements of the Chinese 65th Corps to take the city of
Lashio on the
Burma Road. The fall of
Lashio to the 56th Division on 29 April 1942 cut off much of the local Chinese Army from China and compelled the Allies to evacuate Burma. The Division advanced into Yunnan in pursuit of the Chinese but were halted at the
Battle of Salween River by the Chinese
36th and
88th Divisions on 31 May 1942. Following this success in combat, Watanabe was recalled to Japan, and from 1942 to 1944, was Commandant of the Army School of Science. However, with the war situation rapidly deteriorating against Japan, he was sent to the field again in March 1944 as the first commander in chief of the newly formed
IJA 32nd Army, tasked with the defense of the
Ryukyu Islands. Watanabe was recalled to Tokyo in August the same year, and retired from military service. In the final stages of the war, he was recalled to duty, and assigned as commander of the Osaka region for the expected
American invasion of the Japanese home islands. He was awarded with the
Order of the Rising Sun, 1st class, just before the
surrender of Japan. He died in 1950. ==Decorations==