The Second Sino-Japanese War (July 7, 1937 – September 9, 1945) was a military conflict fought primarily between the Republic of China and the Empire of Japan from 1937 to 1945. The First Sino-Japanese War happened in 1894–95. In January 2017, the Chinese Government extended their official definition of the Second Sino-Japanese War back to September 18, 1931 – the Invasion of Manchuria by Japan – as opposed to the traditional 1937 start date, defined by the Marco Polo Bridge Incident. China fought Japan, with some economic help from Germany, the Soviet Union and the United States. After the Japanese attack on Pearl Harbor in 1941, the war would merge into the greater conflict of World War II as a major front of what is broadly known as the Pacific War. One could call the Second Sino-Japanese War part of World War II, but the latter conflict is still mainly considered to have started in 1939 when France and the British Empire declared war on Nazi Germany following the invasion of Poland. The Second Sino-Japanese War was the largest Asian war in the 20th century. It accounted for the majority of civilian and military casualties in the Pacific War, with anywhere between 10 and 25 million Chinese civilians and over 4 million Chinese and Japanese military personnel dying from war-related violence, famine, and other causes.