BEIJING (REUTERS) - China will bring forward the start date of the country's war with Japan by six years in education textbooks, a move which will bolster patriotic education, state media reported.

The Chinese War Against Japanese Aggression, China's name for its war with Japan, will now be 14 years long, from 1931 to 1945, not the previously taught eight years, China's education ministry told schools on Jan 3.

All classes, textbooks and courses in elementary, middle-schools, high schools and universities will be altered to bring them in line with history experts, said a letter published on Tuesday (Jan 10) on the WeChat account of the People's Daily, the Communist Party's flagship paper.

The changes make the 1931 Mukden incident, an explosion near a Japanese-owned railway line in northern China that led to Japan's invasion and occupation of Manchuria, into the starting point for the war, the People's Daily said.

Previously, the 1937 Marco Polo Bridge Incident, a battle between the Japanese army and China forces near Beijing, had marked the beginning of the war.

Linking the two events makes it clear how the regional occupation of north China's Manchuria later led to the national war, the paper said, adding that the move will also bolster patriotic education.

Sino-Japan relations have long been affected by what China sees as Japan's failure to atone for its war-time aggression.

Japan changed school textbooks in 2016, revising some references to the 1937 Nanjing Massacre, prompting China to lodge an official protest with Japan in March that year.

China says Japanese troops killed 300,000 people in its then capital Nanjing, but a post-war Allied tribunal put the death toll at about half that number and some Japanese conservatives say that accounts of the massacre are a fabrication or exaggerated