Question: When did the war started in which the Type 92 10 cm Cannon was used by the Imperial Japanese Army?
Context: The Mitsubishi Type 92 Reconnaissance Aircraft (九二式偵察機) (company designation 2MR8) was a Japanese short-range reconnaissance aircraft of the 1930s designed by Mitsubishi for the Imperial Japanese Army Air Force.  A total of 230 were built, serving between 1933 and 1936.  A parasol monoplane, the Type 92 was the first military aircraft powered by an engine both designed and manufactured in Japan to enter service. The Second Sino-Japanese War was a military conflict fought primarily between the Republic of China and the Empire of Japan from July 7, 1937 to September 9, 1945.  It began with the Marco Polo Bridge Incident in 1937 in which a dispute between Japanese and Chinese troops escalated into a battle.  The conflict then escalated further into a full-scale war.  It ended with the unconditional surrender of Japan on September 2, 1945 to the Allies of World War II. The Type 38 10 cm Cannon (三八式十糎加農砲 , Sanhachishiki Jissenchi kanonhō ) was a field gun used by the Imperial Japanese Army during World War I, the Second Sino-Japanese War and World War II.  It was a licensed copy of a 1905 Krupp design.  The Type 38 designation was given to this gun as it was accepted in the 38th year of Emperor Meiji's reign (1905).  By 1941 it was thoroughly obsolete and relegated to second-line service. The Type 92 Heavy Armoured Car (九二式重装甲車 , Kyū-ni-shiki Jyū-sōkōsha ) , also known as the Type 92 cavalry tank, was the Empire of Japan's first indigenous tankette.  Designed for use by the cavalry of the Imperial Japanese Army by Ishikawajima Motorcar Manufacturing Company (currently Isuzu Motors), the Type 92 was designed for scouting and infantry support.  Although actually a light tank, it was called "sōkōsha" (armored car) in Japanese due to political sectionalism within the Japanese Army (tanks were controlled by the infantry, whereas the new weapon was intended for the cavalry).  Exactly the same device was used in America with the M1 Combat Car. The Type 92 10 cm Cannon (九二式十糎加農砲 , Kyūni-shiki Jyū-senchi Kannohō ) was a field gun used by the Imperial Japanese Army during the Second Sino-Japanese War and World War II.  The Type 92 number was designated for the year the gun was accepted, 2592 in the Japanese imperial year calendar, or 1932 in the Gregorian calendar.  The Type 92 cannon was intended to supersede the Type 14 10cm Cannon in front line combat service. The Type 92 7.7mm machine gun (九二式七粍七機銃 , Kyūni-shiki nana-miri-nana kijū ) was developed for aerial use for the Imperial Japanese Navy before World War II.  The Type 92 is a light machine gun, and not to be confused with the similarly named Type 92 Heavy Machine Gun. The Type 14 10 cm Cannon (十四式十糎加農砲 , Jyūyon-shiki Kanōhō ) was the first medium caliber cannon totally of Japanese design and the first with a split trail carriage.  The Type 14 designation was given to this gun as it was accepted in the 14th year of Emperor Taishō's reign (1925).  It was used Imperial Japanese Army but was not considered successful and was replaced by the Type 92 10 cm Cannon. The Type 92 battalion gun (九二式歩兵砲 , Kyūni-shiki Hoheihō ) was a light howitzer used by the Imperial Japanese Army during the Second Sino-Japanese War and World War II.  The Type 92 designation was for the year the gun was accepted, 2592 in the Japanese imperial year calendar, or 1932 in the Gregorian calendar.  Each infantry battalion included two Type 92 guns; therefore, the Type 92 was referred to as "battalion artillery" (大隊砲 , Daitaihō ) . The Type 89 15 cm Cannon was the main gun of the Imperial Japanese Army heavy artillery units.  The Type 89 designation was given to this gun as it was accepted in the year 2589 of the Japanese calendar (1929).  It was widely used from the Manchurian Incident to the end of World War II, for example, Nomonhan, Bataan and Corregidor Island, Okinawa.  The Type 89 15 cm gun was comparable to the U.S. M1918 155 mm GPF cannon, but the Type 89 has shorter range.  The Type 89 was less efficient than similar heavy-caliber guns of other nations in World War II. The Type 92 Heavy Machine Gun (九二式重機関銃 , Kyūni-shiki jū-kikanjū ) entered service in 1932 and was the standard Japanese heavy machine gun used during World War II.  It was used extensively by the Imperial Japanese Army and Collaborationist Chinese forces.  Captured weapons were also used extensively by Chinese National Revolutionary Army troops against the Japanese during World War II, and the Korean People's Army against the United Nations forces during the Korean War.  The Type 92 refers to the Japanese Imperial year 2592 – 1932 in the Gregorian calendar – in which the gun entered service.  Designed by Kijiro Nambu and built by Hino Motors and Hitachi, total production was about 45,000 guns.
Answer: July 7, 1937