[3][1] In the middle of August 1939, his unit is sent to Harbin in Manchuria and then at the beginning of September to Saienjo airfield near Nomonhan to participate in the final stages of the Battle of Khalkhin Gol.

However, when he caught up with them he realized he forgot to open the cap on the telescopic sight and had to aim by feeling and was therefore unable to hit them.

In the ensuing air battle he managed to shoot down two Soviet Polikarpov I-15 fighters over Tamsagbulag in Mongolia.

[1][3] At the beginning of autumn 1940, Lieutenant Kurobe and his unit moved to Guangdong in South China in order to support the Japanese invasion of French Indochina.

After the successful evacuation, he again returned to Hankou in Central China where he remained until January 1941, before he was transferred to the Army Academy to serve as an instructor.

[1][3] At the start of the Pacific War, he was promoted to captain and was transferred to the 47th Independent Chūtai, which operated prototype Nakajima Ki-44 fighters.

From December 1941 to March 1942, he was then involved in Malaya Campaign and Battle of Singapore, during which he claimed shooting down three enemy aircraft.