With the start of the Second Sino-Japanese War, Yokoyama was appointed commander of the IJA 2nd Infantry Regiment from March 1938 to March 1939, whereupon he was promoted to major general. He was assigned command of the 2nd Field Railway, followed by the 1st Field Railway until his promotion to lieutenant general in 1941.[1] In June 1942, Yokoyama was assigned command of the Manchukuo-based IJA 8th Division, which was garrisoned in eastern Heilongjiang guarding the border with the Soviet Union. However, in 1944, as the situation in the Pacific War continued to deteriorate for the Japanese, portions of the IJA 8th Division were sent to Truk, where they were largely annihilated by lack of food and American air raids. The remainder of the division was transferred from Manchukuo to the Philippines under the command of General Yamashita Tomoyuki's 14th Area Army, and under the name of “Shimbu Group”, was wholly made responsible for the defense of southern Luzon. Suffering severe casualties, the remnants of the command was assigned to the IJA 41st Army in March 1945. Yokoyama was responsible for defending Manila against the U.S. Sixth and Eighth Armies. Most of the defenders in Manila were the Manila Naval Defense Force, commanded by Adm. Sanji Iwabuchi. While, Gen. Yokoyama retreated to the Sierra Madres to control the hills east of Manila and its water source, the Imperial Japanese Navy's troops held out in Manila. The Shimbu Force would continue fighting after Manila fell in the Battle of Wawa Dam. In 3 months of fighting, the Shimbu Group in the Sierra Madres started off with 40,000 troops was reduced to just 6500 men.[2]
At the end of the war, Yokoyama was arrested, taken before a military tribunal in Manila, and charged with war crimes due to the various atrocities committed by Japanese forces during the Japanese defense of Manila. He was found guilty and sentenced to death.[3] However, Yokoyama's death sentence was never carried out. In July 1953, Yokoyama's death sentence was commuted by President Elpidio Quirino and he was allowed to return to Japan. Yokoyama served another six months at Sugamo Prison before being pardoned entirely in December 1953.[4] In an interview done after his pardon and before his return to Japan, Yokoyama accepted responsibility for what he had allowed to happen and said, "The memory of the destruction and murder committed in the Philippines will remain with me as a nightmare that I will carry to my grave..." He died in 1961.[5]
References
Fukagawa, Hideki (1981). (陸海軍将官人事総覧 (陸軍篇)) Army and Navy General Personnel Directory (Army). Tokyo: Fuyo Shobo. ISBN4829500026.
^Smith, Robert Ross (2014). United States Army in WWII - the Pacific - Triumph in the Philippines. Verdun Press. ISBN978-1515082835.
^von Lingen, Kerstin (2016). War Crimes Trials in the Wake of Decolonization and Cold War in Asia, 1945-1956: Justice in Time of Turmoil. Palgrave Macmillan. p. 163. ISBN978-3319429861.
^"YOKOYAMA Shizuo". The Iola Register. 1953-07-08. p. 5. Retrieved 2022-11-30.