The draft guidelines for the high school history curriculum recently announced by the Ministry of Education have sparked controversy. The part of the curriculum on Taiwan history prompted discussions about the San Francisco Peace Treaty and Cairo Declaration, among other agreements.
After World War II, the legal status of Taiwan was "undetermined." However, after close to 60 years of evolution, the legal status of Taiwan has been "determined."
Today, Taiwan is an independent sovereign country -- although not yet a "normal" country. The treaties and documents relevant to this process of evolution need to be explained from the perspective of public international law.
The San Francisco Peace Treaty is the most authoritative international treaty when it comes to defining the territory of defeated Japan after the World War II. The legal force of this treaty surpassed and replaces the Cairo Declaration and Potsdam Declaration. In the 1943 Cairo Declaration, the heads of the state of the US, Great Britain, and China declared their hope that after the end of the World War II Taiwan and Penghu should be returned to China.
The 1945 Potsdam Declaration stated in Article 8 that the agreement in the Cairo Declaration will be followed.
The San Francisco Treaty, which was signed on September 8, 1951 and then came into force on April 28, 1952 explicitly stated that Japan surrendered the sovereignty and all rights over Taiwan and Penghu. However, it did not state which country was the recipient of the rights and sovereignty handed over by Japan. As a result, Taiwan neither belonged to the Republic of China (ROC) nor the People's Republic of China (PRC). The legal status of Taiwan was therefore undetermined at the time.
This is the basis of the claim that Taiwan's status is yet to be determined. The consensus underlying the San Francisco Peace Treaty was that the undetermined status would be decided when the time comes based on principles outlined in the United Nations (UN) Charter, in particular the right to self-determination and opposition against military aggression. For example, when the US and the ROC signed the bilateral joint-defense treaty in 1954, the US secretary of state at that time emphasized that the legal status of Taiwan would be determined at the appropriate time.
The Cairo Declaration and the Potsdam Declaration were political statements jointly issued by the Allies unilaterally prompted by military needs and in the face of expected victory. Japan, which at the time held sovereignty over the territories in question, did not participate in these declarations. Therefore, they had neither legal force under public international law nor the effect of transferring sovereignty.
On the other hand, the post-war San Francisco Peace Treaty had the participation of both the victorious Allies and also defeated Japan. Through the treaty, the holder of sovereignty over Taiwan and Penghu, Japan, explicitly relinquished sovereignty. Unlike that declaration, in this treaty the need to maintain long-term peace and stability was taken into consideration in addition to military needs.
Under public international law, the end of a warring state between countries requires the signing of a peace treaty. The relinquishment or transfer of territories also require treaties as a legal basis. The legal force of the San Francisco Peace Treaty surpassed the Cairo Declaration and overturned that declaration. No wonder that the Chinese government has always emphasized the importance of the Cairo Declaration in taking the position that Taiwan is part of China, while neglecting to make any mention of the San Francisco Peace Treaty.