If you try to read and understanding, it good point to we discuss continues.
There a lot kind of document on in this world. Some of them have high value, some have low value.
They are depend on International Law, not your Logic. When you bring the letter to international law, it's will consider as a evidence, not highest value and reality it have low value.
1. The Paracel and Spratly archipelagos have been considered Vietnamese territories for many centuries. These islands have both strategic and economic significance, and are now being claimed by many countries including China, Taiwan, the Philippines, Malaysia, and Brunei making it a political hotspot in the region.
This research aims at providing a cumulative, systematic, and detailed picture of the process of establishing Vietnamese sovereignty over the Paracel and Spratly islands.
2. Before 1909, Vietnamese sovereignty over the Paracel and Spratly islands had not been violated by China and other countries. There were not any effort of establishing sovereignty, but there were much documentation of Vietnamese sovereignty in the Paracels.
After 1909 there began to be newspaper articles written about the islands, especially towards the 1920s and early 1930s.
After 1954, these two archipelagos were given to South Vietnam to control according to the Geneva Accord. There was quite a conflict regarding ownership of the islands. As a result a number of significant works were done on the issue.
.....
Please read more
Paracel & Spratly Islands belong to Vietnam - Sovereignty of Vietnam over Spratly and Paracel Islands
And what your Country have? Please show here to discuss.
Now your main point here.
Do you know the situation at this time?
From 1945, after WWII, France back to Vietnam. And for International, Vietnam still the colonized country until Frank Control. And Paracel and Spraty had been under control of France colonized until 1954.
After Dien Bien Phu battle, follow Paris Agreement 1954, Democratic Republic of Vietnam (DRV) controlled North of Vietnam and France controlled South of Vietnam after that France handover South of Vietnam to Republic of Vietnam (RP). RP under supported of American was accepted by Union Nation.
At this moment there were two Governments in Vietnam. And RP was the one who managed Spraty and Paracel. And RP always tolerated any claim of China and bring they ship to occupy Paracel and Spraty. (Remember RP is a Gov accpeted by Union Nation).
The letter of Phan Van Dong (1958) don't said clealy that he accepted China to managed those Island. It's letter and not have value like agreement or contract. Even It's true, DRV is not the Gov who managed those Island at the moment, it was illegal document.
After Vietnam united, the Socialist Republic of Vietnam always tolerate China claim.
And follow UNCLOS, any time in history, the Government of Vietnam who managed Paracel and Spraty always tolerate China claim.
Combine last and this post you can see China is only robber who invade Paracel Island from Vietnam.
Spratly Islands History Timeline
200BC around China firstly discovered the Spratly Islands and other Suthern Sea Islands
111BC China started to occupy and govern the Southern Sea Islands
206BC-24AD Most of the Paracel, the Spratlys and Pratas Island were known by Chinese geographers of the Han Dynasty
23-220AD Yang Fu of the East Han Dynasty made the reference to Nansha Islands in his book entitled Yi Wuzi (Records of Rarities)
220 Nansha (Spratly) Island was settled by Chinese monks, building up a monastery on that island.
220-280AD General Kang Tai one of the famous ancient Chinese navigator of East Wu State of the Three Kingdoms Period mentioned Nansha Islands in his book Funan Zhuan (or Journeys to and from Phnom) (the name of an ancient state in today's Cambodia).
265-420AD Fei Yuan of the Jin Dynasty(265-420 A.D.) wrote about the fishing and collecting of coral samples by the fishermen of China on the South China Sea in his article Chronicles of Guangzhou.
789 The Tang Dynasty, China included the Nansha Islands into its administrative map
990 Spratley Islands became a part of the Northern Song area in Hainan
1121 Kublai Khan controlled most of the islands during China's Yuan Dynasty
1211 The island group shown on a Chinese Map
1250 Chinese frishermen became the right by the Pan-Han Dynasty to settle on some of the northern islets and reefs.
1405 Cheng Ho, the official minister of the Ming Kings, visited several northern islands of the Spartly Islands Group, Cheng Ho made several vojages to the Spratly Group and mapped most of the northern reefs and island, today a reason for China, to occupay the complete group. In 1436 an excellent map of the reefs is shown by the Ming-Dynasty.
1406 - 1444 most of the reefs and islet were successsively maped by Chinese geographers
1478 A China brigg run on Amboya Cay's reef and Archeologists found about 300 ancident vessels, made by ceramics.
1530 Alvarez de Diegoz, one of Albuquerque's navigators found several scattered tiny islets and reefs on his way to the future Macao area
1606 The Spain adventure and sailor Andreas de Pessora reached some of the western Spratly islands and named 'a larger islet' with the name Isla Santa Esmeralda Pequena. Today it is unknown which island Pessora reached, but it could be Spratly Island, or also one of the south-eastern islets.
1710 The Chinese Ching Dynasty claimed two northern islands and errected a small temple on North East Cay.
1730 Pirates settled on several islands and hold up British, Portugese and Dutch ships, crossing the area. In 1735 the British troups runn over and destroyed several priate camps located on some islands.
1791 Captain Spratle arived in the group and named the islands by his name. He was one of Captain Collets navigators.
1798 The British built up an iron observation tower on Itu Aba Islet. The remainds are visible till today.
1804 The British vessel HMS Macclesfield run on a drying reef in the southwest corner of the shoals, known today as the Macclesfield Shoals (Bank)
1883 The Germans wanted to claim several islands in the Spartly Group,
but the Chinese Government threatened with war. After several government notes between Berlin and Peking, Germany gave up Spratly Islands and Paracel Islands but became controller of the area of Tsingtau.
1885 China officially claimed all islands of the Spratly Group
1887 The France built up the first lighttower on Amboyna Cay
1902 Chinese war-ships surveyed and erected sovereignty stone on Paracel Islands.
1908 China gave the right to mine guano from the islands to the British Australian Guano LTD.
1909-03-21 China (Qing Dynasty) set up Paracel Islands administrative committee.
1909-04 China (Qing Dynasty) war-ships surveyed Paracel Islands and affirmed Chinese sovereignty over these islands,
fired cannon and hoisted flag.
1911 China -
Guangdong Government reaffirmed Paracel Islands is under Qiongya (Hainan Island) Adminstration.
1930 French - Japan War over the rights on the Paracel Islands, and some of the north-western Spratley Reefs.
1932-1935 The Chinese Government set up a committee for the review of Maps of Lands and Waters of China. This committee examined and approved the 132 names of the islands in the South China Sea, all of which belong to Xisha, Zhongsha and Nansha Islands.
1933 France raised first official claim to the Paracel and Spratly Islands after invaded and occupied 9 of Nansha Islands, including Taiping and Zhongye.
The Chinese fishermen who lived and worked on the Nansha Islands immediatedly made a firm resistance against the invasion and the Chinese Government lodged a strong protest with the French Government.
1939-44 The Spratly Islands were invaded and occupied by Japan and used as a submarine base during the Second World War. The two major bases were on Itu Aba and on Namyit Island in the Tizard Bank.In line with the Cairo Declaration and the Potsdam Proclamation, the Ministry of Internal Affairs of China, in consultation with the Navy and the government of Guangdong Province, appointed Xiao Ciyi and Mai Yunyu Special Commissioner to the Xisha and Nansha Islands respectively
in 1946 to take over the two archipelagoes and erect marks of sovereignty on the Islands.
1946 China declared the Spratlys as a part of the Guangdong Province, and seized the biggest island of Tai Ping Dao (Itu Aba).
1947 The Ministry of Internal Affairs of China renamed 159 islands, reefs, islets and shoals on the South China Sea, including the Nansha Islands. It subsequently publicized all the names for administrative purposes
1947 The Philippines claimbed some of the eastern islands in the Spratly Group and claimbed too the Scarborough Reef.
1948 The Philippines claimbed the offshore Scarborough Reef, one of the most outlier reefs in the northeastern Spratly Islands. A light was errected and an oberservationtower on the South Rock, a 5 ft high rocky and steep sided islet.
1951 At the San Francisco conference,
Japan renounces all rights to the Spratly Islands.
No resolution is made on who owns them.
1956 The Philippines built up a mailitary base on North Danger Reef.
1961 Taiwan annexed several reefs in the northeastern part of the Spratly Group.
1969 On Spratly Island the American Navy errected a Radar Station, closed in 1971.
1974 China occupies Paracel Islands to the north of the Spratly Islands, taking them from South Vietnam.
1978 China occupies six atolls in the Spratly Islands, taking them from Vietnam.
1979, 21.Dec. Malaysia claimbed Swallow Reef (Layang Layang Reef) and built up a base. In January 1980 Malaysia continued in claimbing and annexed several reefs in the southern and south-western group. A second Malayan station was built on Amboyna Cay, heave disputed with Vietnam
1982 Internatinal conflict between Vietnam and Malysia, when Malaysia claimbed Amboyna Cay.
1984 Brunei claimbed the Louise Reef in the eastern group
1988 Chinese and Vietnamese navies clash at Johnson Reef. Two Vietnamese gunboats are sunk and seventy people die. Chinese troops has been garrisoned on the reef.
1991 Indonesia organises the first of its annual informal meetings (The South China Sea Workshop) of the six claimants to the Spratly Islands to find a peaceful solution to the dispute. Malaysia begins to develop a reef for tourism.
1992 ASEAN nations and China call for restraint in pursuit of territorial claims in the Spratly Islands.
1994,November The US oil giant Exxon signs a US$35 billion deal to develop the gas fields north of Natuna Island. This area is partly claimed by China.
1995,8 February The Philippines's armed forces discover Chinese-constructed concrete markers on Mischief Reef, within 200 kilometres of Palawan Island, in the Philippines.
1995,20-28 March The Philippines seize Chinese fishing boats and crew, and destroy Chinese markers on Mischief Reef.
1995,31 March Taiwanese naval mission of armed patrol boats to the Spratly Islands is called off midway to its destination.
1995, 7 April Indonesia expresses concern over Chinese maps claiming sovereignty over part of the huge Natuna gas fields to the south of the Spratly Islands.
Spratly Islands History Timeline - Nansha Islands of China
------
You guys can't even provide whole history time line for these islands, and can only resort to whinning all over the place like a kid asking for candy.