1. Article 2 of the Treaty of Shimonoseki (1895) ceded Formosa, her dependencies, and the Pescadores from China to Japan in "perpetuity and full sovereignty." Japan's sovereignty over the islands would not be disputed by China or any other state for the next 50 years.

2. In paragraph 3 of the Cairo Declaration (1943), the United States, Great Britain, and China declared that "it is their purpose that Japan shall be stripped of all the islands in the Pacific which she has seized or occupied since the beginning of the First World War in 1914, and that all the territories Japan has stolen from the Chinese, such as Manchuria, Formosa, and the Pescadores, shall be restored to the Republic of China." This and the following two declarations were unilateral statements of intent, not legally binding on the declarants, much less so Japan, the title-holder to Formosa. The Cairo Declaration, intended only as a press release, was issued without signatures. From their language, it is clear that the conference statements are not of the variety of declarations that possess legal force. Indeed, some of the provisions of at least one of the declarations were repudiated by one of the declarants, the United States of America, in her ratification of the Treaty of Peace with Japan.  Moreover, the term "restored" was used in reference to the Republic of China without specifying, though assuming, the Republic of China as the successor to the "Ta Ching Empire," the legal person that had ceded Formosa to Japan. The Republic of China never held possession of Formosa, nor did she claim rights to her until the onset of war with Japan. 

3. The Agreement Regarding Japan contained in the Yalta Declaration (1945) is silent on the disposition of Formosa.

4. Section 3-b(8) of Annex II of the Potsdam Declaration (1945) makes reference to the Cairo Declaration stating "The terms of the Cairo Declaration shall be carried out and Japanese sovereignty shall be limited to the islands of Honshu, Hokkaido, Kyushu, Shikoku and such minor islands as we determine."

5. Under the Instrument of Surrender signed in September 1945 by Japan and the Allies, Japan explicitly accepted the provisions of the Potsdam Declaration, and thus implicitly accepted the provision of the Cairo Declaration "that all the territories Japan has stolen from the Chinese, such as Manchuria, Formosa, and the Pescadores, shall be restored to the Republic of China." The Instrument of Surrender gave legal effect to the Allied Conference Declarations hitherto absent. However, the Instrument was a record only of provisional arrangements, a modus vivendi, that anticipated replacement by a more permanent and detailed settlement. The Instrument required no ratification and does not have the legal force of a treaty.

6. The Surrender Order of the Japanese Imperial General Headquarters (1945), issued pursuant to instructions from the Supreme Commander for the Allied Powers, gave authority to Chiang Kai-shek to accept the surrender of Japanese Forces "within China (excluding Manchuria), Formosa, and French Indochina north of 16 degrees north latitude." This authority did not contemplate a transfer of sovereignty in any of the areas indicated. For a fuller discussion, see here.  

8. The Treaty of Peace between the Republic of China and Japan (1952) again left open the question of sovereignty over Formosa. Article 2 of the Treaty merely recognises Japan's renunciation of sovereignty under the San Francisco Treaty. Article 2 was not a new renunciation. Article 4 of the Treaty does, however, abrogate all agreements between China and Japan concluded before 9 December 1941. This would include the Shimonoseki Treaty and would implicitly nullify the cession of Formosa to Japan. Note here the precision of the language: It is the agreements between China and Japan, and not only between the Republic of China and Japan that are nullified. This stands in stark contrast to the ambiguity of the language contained in the Cairo Declaration. Despite this abrogation, the absence of a specific provision transferring sovereignty to China is striking, especially in light of Article 5 which abrogates a specific agreement between Japan and China. It should also be noted that when Japan restored the Liaotung Peninsula (the other territory transferred under the Shimonoseki Treaty) to China, the restoration was explicitly effected by a new treaty, the Liaotung Convention (1895). The Treaty of Peace between the Republic of China and Japan points to both the San Francisco Treaty (Article 11) and the Charter of the United Nations (Article 6) as guides for their relationship and for the settlement of disputes.

9. The Treaty of Peace and Friendship between Japan and the People's Republic of China (1978) was not a peace treaty. It did not terminate a state of war nor settle any other issues, but rather contained in five short articles general commitments to good-neighbourliness. The Treaty is silent on Formosa, though it alludes to the Joint Communiqué of the Government of Japan and the Government of the People's Republic of China (1972).

10. Neither Japan nor the United States of America has ever recognised Chinese sovereignty over Formosa. In their respective Joint Communiqués with the People's Republic of China normalising relations with the latter regime, both Japan and the United States of America merely acknowledge the Chinese position, without concurring with it. The language is very precise. Item 3 of the Joint Communiqué of the Government of Japan and the Government of the People's Republic of China (1972) states only that Japan "understands" the Chinese position and item 7 of the Joint Communiqué between the United States of America and the People's Republic of China (1979) states only that the United States "acknowledges" the Chinese position.

11. Despite the Government of the Republic of China's use of the term "retrocession" to describe Chiang Kai-shek's assumption of control over Formosa in 1945, neither "retrocession" nor any other term used to describe a transfer of sovereignty is ever mentioned in any of the post-war agreements dealing with Formosa. In fact, any such language seems to have been studiously avoided by both China's allies and Japan. An examination of the post-war agreements shows how meticulous the parties were in all other matters, so the absence of a provision for transfer cannot be deemed an oversight. By contrast, the Liaotung Convention repeatedly uses forms of the term "retrocession" in reference to the transfer of sovereignty of the Liaotung Peninsula to China.

12. Until 1943, the Chinese Communist Party consistently recognised the Taiwanese as a distinct "nation" or "nationality" (minzu). It acknowledged the "national liberation movement" on Taiwan as a struggle of a "weak and small minority" (ruoxiao minzu) separate from the Chinese Revolution and potentially sovereign. After 1943, particularly after the Cairo Conference, the Party reversed positions by disavowing Taiwanese ethnic separateness and rejecting the independence of political movements on the island. (see Hsiao, F.T. and Sullivan, L.R. "The Chinese Communist Party and the Status of Taiwan, 1928-1943" Pacific Affairs, volume 52 issue 3 (Autumn 1979), pp. 446-467).

13. The conclusion of formal agreements between states is not the only means of establishing sovereignty. There are several methods of acquiring sovereignty recognised by international law. Self-determination and prescription are the principles most relevant in the case of Taiwan. Because of the unusual circumstances surrounding Chiang Kai-shek's occupation of Taiwan in 1945 and Japan's renunciation of sovereignty over the island in 1952, it is as difficult determining whether sovereignty over Taiwan has been established since 1945 by internationally acceptable means as it is in determining the island's legal status based solely on formal international agreements. International legal practice must be taken in concert with formal agreements when examining the legal basis for Taiwan's status.

14. Taiwan meets all the qualifications for statehood as defined by Article 1 of the Montevideo Convention on the Rights and Duties of States (1933), which states: "The state as a person of international law should possess the following qualifications: (a) a permanent population; (b) a defined territory; (c) government; and (d) capacity to enter into relations with the other states." Her lack of diplomatic recognition notwithstanding, Taiwan is a sovereign state, both de facto and de jure, based on these criteria. The dispute over Taiwan's status is a matter of politics and not of law. 

15. Conclusion: Japan held undisputed sovereignty over Formosa from 1895 to 1945. After Japan's defeat in war in 1945, Formosa's surrender was accepted and the island occupied by representatives of Chiang Kai-shek, as Supreme Commander of Allied Forces in the China Theatre. In 1951, Japan renounced sovereignty over the island without making provision for a transfer of sovereignty. The Treaty of Peace in which Japan renounced sovereignty over Formosa declared Japan's commitment to the principles of the United Nations Charter, which includes a commitment to self-determination of peoples and which implicitly transferred sovereignty over the island to her inhabitants. In the absence of formal agreements regarding sovereignty over territory, current international law favours self-determination as the means of establishing sovereignty. No other agreement since the 1951 Treaty has clarified the issue of sovereignty over Formosa. Constitutional reforms in the Republic of China in the 1990s transformed the regime on Formosa from an occupation government into a democratic government representative of the will of the people of Formosa. The only state which currently disputes the Formosan people's sovereignty over the island is the People's Republic of China, a state which has never held possession or title to the island and whose leadership prior to 1943 supported the "national liberation struggle" on the island.