Question: What month did the unit of the Imperial Japanese Army that undertook lethal human experimentation during the Second Sino-Japanese War got pardon?

Context paragraphs:
102nd Infantry Regiment (Imperial Japanese Army): The 102nd Infantry Regiment was an infantry regiment in the Imperial Japanese Army.  The regiment was at one stage attached to the 128th Infantry Brigade, of the 114th Division, in the Tenth Army during the Second Sino-Japanese War.  The regiment was later attached to the Eastern District Army on 7 September 1940, then the Kwantung Army on 1 August 1941, then assigned to the Twenty-Third Army on 19 September 1941 and the Eighteenth Army in November 1942.  The regiment participated during the Second Sino-Japanese War and during the later stages of World War II, the regiment was in New Guinea, taking part in the New Guinea campaign.

Battle of Wuhan: The Battle of Wuhan, popularly known to the Chinese as the Defense of Wuhan, and to the Japanese as the Capture of Wuhan, was a large-scale battle of the Second Sino-Japanese War.  Engagements took place across vast areas of Anhui, Henan, Jiangxi, Zhejiang, and Hubei provinces over a period of four and a half months.  This battle was the longest, largest and arguably the most significant battle in the early stages of the Second Sino-Japanese War.  More than one million National Revolutionary Army troops from the Fifth and Ninth War Zone were put under the direct command of Chiang Kai-shek, defending Wuhan from the Central China Area Army of the Imperial Japanese Army led by Shunroku Hata.  Chinese forces were also supported by the Soviet Volunteer Group, a group of volunteer pilots from the Soviet Air Forces.

Shigeyasu Suzuki: Shigeyasu Suzuki (鈴木 重康 , Suzuki Shigeyasu , 1 September 1886 – 11 June 1957) was a lieutenant general in the Imperial Japanese Army during the early part of the Second Sino-Japanese War.  His brother, Suzuki Minoru was a major general in the Imperial Japanese Army Medical Corps.

Nanking Massacre denial: Nanking Massacre denial is the denial that Imperial Japanese forces murdered hundreds of thousands of Chinese soldiers and civilians during the Second Sino-Japanese War, a highly controversial episode in Sino-Japanese relations.  It is considered a revisionist viewpoint and is not accepted in mainstream academia, even within some Japanese academia.  Most historians accept the findings of the Tokyo tribunal with respect to the scope and nature of the atrocities committed by the Imperial Japanese Army after the Battle of Nanking.  In Japan, however, there has been a heated debate over the extent and nature of the massacre.  Relations between Japan and China have been complicated as a result, as denial of the massacre is seen as part of an overall unwillingness on Japan's part to admit and apologize for its aggression, or a perceived insensitivity regarding the killings.  Estimates of the death toll vary widely, ranging from 40,000 to over 300,000.  Some scholars, notably the revisionists in Japan, have contended that the actual death toll is far lower, or even that the event was entirely fabricated and never occurred at all.  These revisionist accounts of the killings have become a staple of Japanese nationalist discourse.

Zhang Zizhong: Zhang Zizhong (; August 11, 1891 – May 16, 1940) was a general of the Chinese National Revolutionary Army (NRA) during the Second Sino-Japanese War.  Born in Linqing, Shandong, he was the highest-ranked officer and the only Army group commander of the NRA to die in the war.  He showed great valor in the battlefields and was regarded as one of the most valiant and respectable Chinese generals by the Imperial Japanese Army during the Second Sino-Japanese War.  Because of his posthumous promotion, he was also one of the highest-ranked Allied officers that was killed in action in World War II.  His mausoleum is situated in Beibei District, Chongqing.  There are roads named after him in Shanghai, Beijing and Tianjin.

Unit 731: Unit 731 (Japanese: 731部隊 , Hepburn: Nana-san-ichi Butai ) was a covert biological and chemical warfare research and development unit of the Imperial Japanese Army that undertook lethal human experimentation during the Second Sino-Japanese War (1937–1945) of World War II.  It was responsible for some of the most notorious war crimes carried out by Japan.  Unit 731 was based at the Pingfang district of Harbin, the largest city in the Japanese puppet state of Manchukuo (now Northeast China).

Kawasaki Ki-10: The Kawasaki Ki-10 (九五式戦闘機 , Kyūgo-shiki sentōki , Army Type 95 Fighter) was the last biplane fighter used by the Imperial Japanese Army, entering service in 1935.  Built by Kawasaki Kōkūki Kōgyō K.K. for the Imperial Japanese Army, it saw combat service in Manchukuo and in north China during the early stages of the Second Sino-Japanese War.  Its reporting name given by the Allies was "Perry".

American cover-up of Japanese war crimes: The American cover-up of Japanese war crimes occurred after the end of World War II, when the occupying US government granted political immunity to military personnel who had engaged in human experimentation and other crimes against humanity, predominantly in mainland China.  The pardon of Japanese war criminals, among whom were Unit 731's commanding officers General Shiro Ishii and General Masaji Kitano, was overseen by General of the Army Douglas MacArthur in September 1945.  While a series of war tribunals and trials was organized, many of the high-ranking officials and doctors who devised and respectively performed the experiments were pardoned and never brought to justice.  As many as 12,000 people, most of them Chinese, died in Unit 731 alone and many more died in other facilities, such as Unit 100 and in field experiments throughout Manchuria.

Shirō Ishii: Surgeon General Shirō Ishii (石井 四郎 , Ishii Shirō , ; June 25, 1892 – October 9, 1959) was a Japanese army medical officer, microbiologist and the director of Unit 731, a biological warfare unit of the Imperial Japanese Army involved in forced and frequently lethal human experimentation during the Second Sino-Japanese War (1937–1945).

He Chengjun: He Chengjun () (June 20, 1882 – May 7, 1961) was a Kuomintang politician and military officer of the Republic of China.  He was born in Hubei.  He was graduate of the Imperial Japanese Army Academy.  As a member of the Tongmenghui, he took part in the Xinhai Revolution.  He was briefly mayor of Beijing after its capture by the National Revolutionary Army during the Northern Expedition.  In the Second Sino-Japanese War, he was governor of his home province and defended it against the advancing Imperial Japanese Army.  After the defeat of the Kuomintang in the Chinese Civil War, he went to Hong Kong and in 1951 arrived in Taiwan.  He died in Taipei at the age of 78.

Supporting paragraphs: American cover-up of Japanese war crimes Unit 731
Answer: September