Indeed, Japan turned its military attention to Soviet territories. Conflicts between the Japanese and the Soviets frequently happened on the border of Manchuria between 1938 and 1945. The first confrontation occurred in Primorsky Krai, the Battle of Lake Khasan (July–August 1938) involved an attempted military incursion of Japanese-controlled Manchukuo into territory claimed by the Soviet Union. This incursion was founded in the beliefs of the Japanese side that the Soviet Union had misinterpreted the demarcation of the boundary based on the 1860 Treaty of Peking between Imperial Russia and Manchu China. Primorsky Krai was always threatened by a Japanese invasion despite the fact that most of the remaining clashes occurred in Manchukuo.