Sino-Soviet conflict (1929)

Sino-Soviet conflict (1929)
	Part of interwar period
	; Soviet soldiers with captured Kuomintang banners.
Date	July – December 1929
Location	Manchuria
Result	Soviet victory Provisions of 1924 agreement upheld; Khabarovsk Protocol signed; The Soviet/Russian military occupation over entire Bolshoy Ussuriysky Island until 2004 ;
Belligerents
Republic of China; White movement of Russia	Soviet Union
Commanders and leaders
Zhang Xueliang	Vasily Blyukher; Kliment Voroshilov
Units involved
Northeastern Army White émigré volunteers; White guerrilla groups Nazarov detachment; Dutov-Pozdnikov White Guard band; Nechaev detachment;	Special Red Banner Far Eastern Army 18th Rifle Corps; 19th Rifle Corps; 21st Rifle Division; 12th Rifle Division; OGPU detachments; Soviet Air Forces detachments; Soviet Navy and border guard detachments
Strength
c. 200,000 3,000+ White Russians;	c. 113,000 (peak)
Casualties and losses
Official Chinese accounts:; 2,000 killed, 1,000 wounded, 8,550 captured; Modern estimate:; c. 5,000 lost	Official Soviet accounts:; 812 killed, 665 wounded, 4 missing; Modern estimate:; Far more than officially reported

The Sino-Soviet conflict of 1929 (Chinese: 中東路事件, Russian: Конфликт на Китайско-Восточной железной дороге) was an armed conflict between the Soviet Union and the Chinese warlord Zhang Xueliang of the Republic of China over the Chinese Eastern Railway (also known as the CER).

The conflict was the first major combat test of the reformed Soviet Red Army, which was organized along the latest professional lines, and ended with the mobilization and deployment of 156,000 troops to the Manchurian border. Combining the active-duty strength of the Red Army and border guards with the call-up of the Far East reserves, approximately one in five Soviet soldiers was sent to the frontier, the largest Red Army combat force to be fielded between the Russian Civil War (1917–1922) and the Soviet Union's entry to the Winter War (1939-1940).

In 1929, the Chinese Northeastern Army took over the Chinese Eastern Railway to regain sole control of it. The Soviet Union quickly responded with a military intervention and eventually forced the Chinese to return the railway to the previous format of joint administration. During the conflict, the Soviets gained full control of Bolshoy Ussuriysky Island (Chinese: 黑瞎子岛) from China, and its military occupation of the island continued until the 1991 Sino-Soviet Border Agreement, in which Russia agreed to return the western half of the island to China in 2004.