So, what exactly is the “One China” principle that Beijing asserts? Can the Taiwan issue truly be called “China's internal affair”? I would like to trace the historical background once again.
The fundamental document governing relations between Tokyo and Beijing has been the Japan-China Joint Communique issued at the time of the normalization of bilateral diplomatic relations in 1972. Its third paragraph stipulates the following: [4]
“The Government of the People's Republic of China reiterates that Taiwan is an inalienable part of the territory of the People's Republic of China. The Government of Japan fully understands and respects this stand of the Government of the People's Republic of China, and it firmly maintains its stand under Article 8 of the Potsdam Proclamation.”
What China insisted on during the normalization of diplomatic ties was its position that “Taiwan is an inalienable part of the territory of the People's Republic of China.” However, Japan neither agreed to nor accepted this position. That is precisely why, unlike other paragraphs written in a form indicating “mutual agreement,” the third paragraph ultimately took the form of presenting both sides' respective positions side by side.
Then, why was Japan unable to agree? There were both legal and political reasons for this. [5]
Legally, Japan had already renounced its sovereignty over Taiwan under the San Francisco Peace Treaty, which came into effect in 1952. Japan therefore adopted a reserved position: “The question of where Taiwan, renounced under the San Francisco Peace Treaty, should belong is a matter to be decided primarily by the Allied Powers, and Japan is not in a position to make any statement on it.”
The above-mentioned phrase “fully understands and respects” goes further than the wording used in the Shanghai Communique between the United States and China—namely “acknowledge.” However, China was not satisfied only with this formulation. In the end, agreement was reportedly reached by adding the wording, “and maintains its stand under Article 8 of the Potsdam Declaration.” [6]
Article 8 of the Potsdam Declaration states that “the terms of the Cairo Declaration shall be carried out,” and the Cairo Declaration provides 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.” By adding this clause, Japan allowed China to interpret the statement as Japan recognizing “the return of Taiwan to the Republic of China.” From Japan's perspective, however, it is possible to explain that this merely reiterated the Potsdam Declaration, which Japan had already accepted.
More fundamentally, there was the concern that if Japan were to plainly acknowledge China's claim that Taiwan is an inalienable part of Chinese territory, it would amount to recognizing the legitimacy of China's position that it holds the ultimate right to liberate Taiwan by force. [7]
Another factor was political considerations involving the United States. A major diplomatic priority for the Japanese government in 1972 was the reversion of sovereignty over Okinawa. The United States was greatly concerned that, once Okinawa was returned to Japan, it might no longer be able to use the bases there as freely as it had under U.S. administration. More specifically, it was Washington's desire that it wanted to ensure that no restrictions would arise on the use of U.S. bases in Okinawa in the event of situations such as a North Korean armed attack or China's use of force to unify Taiwan.
In response to this, the Sato-Nixon Joint Statement of November 1969 noted that “the President referred to the treaty obligations of his country toward the Republic of China which the United States would uphold,” while Prime Minister Sato expressed his view that “the maintenance of peace and security in the Taiwan area is also a most important factor for the security of Japan.” It was precisely this political context that formed the background for settling on the wording “fully understands and respects.” [8] Japan could not agree to anything that might undermine the US position of defending Taiwan, which belonged to the free world.
It is for this reason that the Japanese government's unified view expressed by Foreign Minister Ohira during the 1973 House of Representatives Budget Committee session is of particular significance—especially the phrase “basically” as mentioned in his view: “We consider the issue of confrontation between the People's Republic of China and Taiwan to be, basically, a domestic issue of China.” The inclusion of “basically” conveys an important nuance. [9]
Takakazu Kuriyama, a career diplomat responsible for treaties at the Foreign Ministry then, made this point explicitly by going as far as to say: “The Taiwan issue is something that should be resolved through dialogue between the two parties across the Taiwan Strait, and the Japanese government has no intention of intervening in any way...(omitted)...However, if China were, even in the most unlikely scenario, to resort to the use of force to unify Taiwan (or what is called “liberation by force”), then this could no longer be considered a domestic matter. That is the meaning of the phrase basically.” His observation is one that we should continue to keep firmly in mind today.