HistoryData
Historical ConflictChina

Second Sino-Japanese War

The largest Asian war of the 20th century, it caused roughly 20 million deaths and determined China's postwar status as a founding UN Security Council member.

Duration & Scope

1937 1945

8 years

Estimated Total Casualties

20.0M

Key Facts

Duration
8 years (1937–1945)
Total deaths
~20 million, mostly Chinese civilians
Biological warfare deaths
At least 200,000
Conflict start (Manchuria)
18 September 1931 (Mukden Incident)
Full-scale war began
7 July 1937 (Marco Polo Bridge Incident)

Strategic Narrative Overview

Japan rapidly captured Shanghai and Nanjing, perpetrating the Nanjing Massacre. By 1938 Wuhan had fallen, pushing the Nationalist government to Chongqing. Soviet aid sustained Chinese forces until the 1941 Soviet-Japanese Neutrality Pact ended it. After Pearl Harbor, the United States became China's principal backer via Lend-Lease. A stalemate persisted until Japan launched Operation Ichi-Go in 1944; China responded with counteroffensives in South China and the completion of the Ledo Road supply route in 1945.

01 / The Origins

Japan's expansionist ambitions in Asia led to the staged Mukden Incident in 1931, justifying the seizure of Manchuria and creation of the puppet state Manchukuo. Skirmishes continued through the early 1930s while China was internally divided by civil war between Nationalist and Communist forces. Facing imminent full invasion, Chiang Kai-shek and the Communists formed a United Front in 1936, but Japan escalated hostilities at the Marco Polo Bridge in July 1937, triggering all-out war.

03 / The Outcome

Japan surrendered on 2 September 1945 following the atomic bombings of Hiroshima and Nagasaki and the Soviet invasion of Manchuria. China regained Taiwan and achieved recognition as one of the Big Four Allied powers, securing a permanent seat on the UN Security Council. The wartime United Front dissolved almost immediately, and the Chinese Civil War resumed in 1946, eventually ending with Communist victory and the founding of the People's Republic.

Belligerents & Mobilization Analysis

Side A

1 belligerent

Empire of Japan
Key Commanders

Hideki Tojo, Shunroku Hata.

Side B

4 belligerents

Republic of China (Nationalist)Chinese Communist Party forcesSoviet Union (1945)United States (support/Lend-Lease)
Key Commanders

Chiang Kai-shek, Mao Zedong, Zhu De.

Total Casualties (all sides)
20,000,000
Outcome
Japanese defeat; China recognized as major Allied power and founding UN Security Council permanent member; Taiwan returned to China

Kinetic Engagement Axis

Major engagements timeline (1937–1945)Timeline of major military engagements plotted chronologically.193719451931Mukden IncidentAllied1937Battle of ShanghaiAllied1937Battle of NanjingAllied1938Battle of WuhanAllied1939Battle of Changs…Side B1940Hundred Regiment…Side B1944Operation Ichi-GoAllied1945Battle of West H…Side B1945Burma Campaign /…Side B

Scroll horizontally to view full axis. Events plotted relatively.

Side A victorySide B victoryInconclusiveDecisive / turning point

Location

Map of ChinaMap of ChinaChina