While no armed conflicts have broken out between Japan and China since WW II, a lot of distrust and animosity remain, partly as leftovers from the Japanese invasion and occupation of China between 1928-1945.
The series of wars between and conflicts between China and Japan are known as the Sino-Japanese Wars. These wars weakened China, while helping Japan gain more power, until the final war in which China finally gained allies to finish WW II.
In the First Sino-Japanese War (1894-1895), the conflict between China and Japan took place over who would control Korea. Japan would rule Korea for 50 years, until the end of WW II in 1945, when Korea got divided in North and South along the 38th parallel north.
After the Boxer Rebellion between 1899-1901, a Chinese secret society called the “Boxers’ began an uprising to drive out Western influence from China. After Chinese rebels and military started a siege to oust the foreign embassies, in the capital of Peking (now called Beijing), an alliance of 8 Western nations gathered 45.000 military forces to invade and annex China. China was forced to pay the total financial costs of the conflict and accept more foreign troops on their soil.
The Japanese Army invaded the Chinese province of Manchuria (1931-1932), setting up a puppet government to control the great natural resources in this northern part of China. Some historians date the beginning of WW II to the beginning of the Japanese takeover of Manchuria. Later, Japanese forces advanced to occupy Jehol, near the Mongolian border.
During the Second Sino-Japanese War (1937-1945), Japan launched an all out invasion of China. Since 1945, Japan and China have not fought a war against each other.
In November 2013, China declared a large swath of sea & air off the Chinese coast, as a new Air Defense Identification Zone (ADIZ), requiring foreign ships and planes to log travel plans with the Chinese authorities.
The USA immediately escalated the conflict and responded with trespassing an overflight with two B-52 bombers, followed by overflights by both South Korean and Japanese military planes. The ongoing tensions are serious, and a wrong move or accidental clash could develop into a new war between Japan and China.
History Guy.com / AA Magnum News 2017.