Q&A: China-Japan islands row
Ties between China and Japan have been repeatedly strained by a territorial row over a group of islands, known as the Senkaku islands in Japan and the Diaoyu islands in China.What is the row about?
At the heart of the dispute are eight uninhabited islands and rocks in the East China Sea. They have a total area of about 7 sq km and lie north-east of Taiwan, east of the Chinese mainland and south-west of Japan's southern-most prefecture, Okinawa. The islands are controlled by Japan.
They matter because they are close to important shipping lanes, offer rich fishing grounds and lie near potential oil and gas reserves. They are also in a strategically significant position, amid rising competition between the US and China for military primacy in the Asia-Pacific region.What is Japan's claim?
Japan says it surveyed the islands for 10 years in 19th Century and determined that they were uninhabited. On 14 January 1895 Japan erected a sovereignty marker and formally incorporated the islands into Japanese territory as part of the Nansei Shoto islands.
After World War Two, Japan renounced claims to a number of territories and islands including Taiwan in the 1951 Treaty of San Francisco. The Nansei Shoto islands came under US trusteeship, being returned to Japan in 1971 under the Okinawa reversion deal.
Japan says China raised no objections to the San Francisco deal. And it says that it is only since the 1970s, when the issue of oil resources in the area emerged, that Chinese and Taiwanese authorities began pressing their claims.What is China's claim?
China says that the Diaoyu islands have been part of its territory since ancient times, serving as important fishing grounds administered by the province of Taiwan. The Ministry of Foreign Affairs has said that this is "fully proven by history and is legally well-founded".
Taiwan was ceded to Japan in the Treaty of Shimonoseki in 1895, after the Sino-Japanese war.
When Taiwan was returned in the Treaty of San Francisco, China says the islands should also have been returned. But Beijing says Kuomintang leader Chiang Kai-shek did not raise the issue, even when the Diaoyu islands were named in the later Okinawa reversion deal, because he depended on the US for support.
Separately, Taiwan also claims the islands.How have they pressed their claims?
Japan controls the islands, and its coast guards patrol the surrounding waters. But actions by nationalist activists on both sides have repeatedly exacerbated tension.
In 1996 a Japanese group established a lighthouse on one of the islands. Chinese activists then sailed repeatedly to the islands and in one incident, Hong Kong activist David Chan jumped into the sea and drowned. Since then, there have been periodic attempts by Chinese and Taiwanese activists to sail to the islands.
There have also been face-offs between Japanese patrol boats and Chinese or Taiwanese fishing vessels. In 2005, 50 Taiwanese fishing boats staged a protest in the area, complaining of harassment by Japanese patrols.
In September 2010, Japan seized a Chinese trawler and its crew after it collided with two coast guard vessels near the islands, sparking a serious diplomatic row. Small anti-Japanese protests were held in several cities in China. In the end, Japan released the trawler's crew.
In April 2012, a fresh row ensued after outspoken Tokyo Governor Shintaro Ishihara said he would use public money to buy the islands from their private Japanese owner.
Amid visits to the islands by Japanese and Hong Kong activists, the Japanese government then reached a deal to buy three of the islands from the owner in a move to block Mr Ishihara's more provocative plan.
The move angered China, triggering small protests and hitting the operations of some Japanese firms in China. Since then, Chinese government ships have sailed in and out of what Japan says are its territorial waters around the islands on many occasions.Has the row been limited to spats at sea?
No. Both sides have taken their dispute to the air, rolling it into a broader regional power struggle.
Japan has complained of Chinese unmanned drones flying near its airspace and has scrambled jets as a deterrent.
Japan's Defence Ministry appeared to float the idea in October 2013 that it had the right to shoot down foreign drones approaching its airspace, sparking an angry reaction from Beijing.
Periodic crises have also been caused by Chinese government planes straying too close to the disputed islands for Japan's liking.
In November 2013, China announced the creation of a new air-defence identification zone, which would demand any aircraft in the zone to comply with a number of rules laid down by Beijing.
The area covers the airspace above the disputed islands, and also overlaps with Japan's claimed air-defence zone. Japan labelled the move a "unilateral escalation".What is the role of the US?
The US and Japan forged a security alliance in the wake of World War II and formalised it in 1960. Under the deal, the US is given military bases in Japan in return for its promise to defend Japan in the event of an attack.
This means - in theory - that if conflict were to erupt between China and Japan, Japan would expect US military back-up. Some US analysts, however, have pointed out that intervention in any Japan-China islands clash is not in America's interests.
The US continues to express vocal support for the Japan-US alliance and - on the islands row - has called for cool heads to prevail, warning of the high stakes involved in any potential escalation.What next?
The Senkaku/Diaoyu issue complicates efforts by Japan and China to resolve a dispute over oil and gas fields in the East China Sea that they both claim.
It also highlights the more robust attitude China has been taking to its territorial claims in both the East China Sea and the South China Sea. And it poses worrying questions about regional security as China's military modernises as the US embarks on its "pivot" to Asia.
In both China and Japan, meanwhile, the dispute has a tendency to ignite nationalist passions on both sides, putting pressure on politicians to appear tough and ultimately making any possible resolution even harder to find.