Following the defeat of Japan at the end of World War II, the Republic of China re-claimed the entirety of the Paracels, Pratas and Spratly Islands after accepting the Japanese surrender of the islands based on the Cairo and Potsdam Declarations. In November 1946, the Republic of China sent naval ships to take control of these islands after the surrender of Japan.
The nine-dotted line was originally an eleven-dotted-line first shown on a map published by the Kuomintang government of the Republic of China (1912–1949) in December 1947 to justify its claims in the South China Sea. After the Communist Party of China took over mainland China and formed the People's Republic of China in 1949, the line was adopted and revised to nine as endorsed by Zhou Enlai. After evacuating to Taiwan, the Republic of China has continued its claims, and the nine-dotted line remains as the rationale for Taiwan's claims to the Spratly and Paracel Islands.
This is China's 2009 nine-dash map submission to the UN that heightened the regional dispute. The map here is the second page in a two-page document. The first page is a text addressed to the UN Secretary General, noting China's sovereignty claim to the "islands in the South China Sea and the adjacent waters", however, the document remains ambiguous by being silent as to the precise meaning of the map enclosed, and the meaning of the nine-dash line on it.
The nine-dotted line has been used by China to show the maximum extent of its claim without indicating how the dots would be joined if it was continuous and how that would affect the extent of the area claimed by China. The Philippines, Vietnam, Malaysia, Brunei and Indonesia have all officially protested over the use of such a line. Immediately after China submitted a map to the UN including the 9-dotted lines territorial claim in the South China Sea on May 7, 2009, the Philippines lodged a diplomatic protest against China for claiming the whole of South China Sea illegally. Vietnam and Malaysia filed their joint protest a day after China submitted its 9-dash line map to the UN. Indonesia also registered its protest, even though it did not have a claim on the South China Sea.
It is reported that in 2013 the PRC extended their claims with a new ten-dash map, but in fact the "new" dash is to the east of Taiwan, not in the South China Sea.[1