The territorial dispute between China and Japan over a cluster of islands in the East China Sea is about fishing reserves, energy resources and national egos, but there's a history of uneasy relations between the two superpowers that dates back more than a century.
Here are seven key moments in modern history that have shaped Sino-Japanese diplomatic relations and brought the countries to such a precarious point that on Sunday, anti-Japanese demonstrations broke out in more than 20 Chinese cities.
1895: China relinquishes control of Taiwan to Japan after the first Sino-Japanese war. Japan later gives up its claim.
1937: Japan invades China and seizes Shanghai and Beijing. The Imperial Japanese Army enters Nanjing on Dec. 13 and slaughters children, rapes women and kills more than 250,000 people in what is now known as the “Rape of Nanjing.”
1972: Despite anti-Japanese demonstrations throughout China, Japan’s prime minister visits China and diplomatic relations stabilize.
2001: Japan's Prime Minister Junichiro Koizumi visits the Yasukuni Shrine, a dedication to the country's fallen soldiers. His visit is seen by many Chinese as symbolizing a denial of Japan's World Word II war crimes, specifically the Rape of Nanjing.
2005: Relations deteriorate after Japanese textbooks understate Rape of Nanjing atrocities. Violent anti-Japanese protests erupt throughout China, North Korea, South Korea and other Asian nations.
2010: Japan arrests captain Zhan Qixiong and 14 crewmen who were fishing too close to the disputed Senkaku/Diaoyu islands. Japan frees the crew, but refuses to apologize.
2012: A series of chess moves by China and Japan over the Senkaku/Diaoyu islands frays already fragile relations. On Aug. 15, Japanese police arrested China activists who had sailed to the islands. On Aug. 19, Japanese activists landed on the islands without permission.
On Monday, the US announced a planned deployment of a second advanced missile-defense radar system on Japanese territory. China strongly criticized the military maneuver.
The defense system is ostensibly a deterrent against North Korea, but Shi Yinhong, professor of international studies at Renmin University, told The New York Times, “The joint missile defense system objectively encourages Japan to keep an aggressive position in the Diaoyu Islands dispute, which sends China a very negative message."
He added, "Japan would not have been so aggressive without the support and actions of the US.”