The Soviet Union did not sign the Treaty of Peace with Japan in 1951. On October 19, 1956, Japan and the Soviet Union signed a Joint Declaration providing for the end of the state of war and for the restoration of diplomatic relations between both countries. They also agreed to continue negotiations for a peace treaty. In addition, the Soviet Union pledged to support Japan for UN membership and to waive all World War II reparations claims. The joint declaration was accompanied by a trade protocol, which granted reciprocal most favored nation status and provided for the development of trade. Japan derived few apparent gains from the normalization of diplomatic relations. The second half of the 1950s saw an increase in cultural exchanges. Territorial provisions The Joint Declaration provided in Article 9 for the continuation of negotiations for the conclusion of a peace treaty after the restoration of diplomatic relations between the countries and further stipulated that "in this connexion, the Union of Soviet Socialist Republics, desiring to meet the wishes of Japan and taking into consideration the interests of the Japanese State, agrees to transfer to Japan the Habomai Islands and the island of Shikoton, the actual transfer of these islands to Japan to take place after the conclusion of a Peace Treaty between the Union of Soviet Socialist Republics and Japan." At the time, the United States threatened to keep the Ryukyu Islands if Japan gave away the other islands, which prevented the negotiation of the promised treaty. Moreover, the clause was supposedly based upon agreement between the two nations, but each came to interpret it differently. The Soviet Union maintained that the territorial problem had been closed and that territorial demarcation would not be discussed beyond the promised transfer of two islands. When the Japanese tried to include a passage "including territorial issue" in a sentence regarding continuation of the negotiations, the Soviets refused, explicitly stating that it did so precisely to avoid interpretation that would suggest other "territorial questions" beyond Shikotan-Habomai issue. The Japanese agreed to drop the expression but had a different interpretation arrived anyway. When the final agreement had been reached on the terms of the Joint Declaration, the Japanese delegation decided to interpret it as including a discussion of the territorial problem in the future peace negotiation by interpreting the declaration jointly with "Hatoyama-Bulganin letters" and "Matsumoto-Gromyko letters". Exchanged before the final negotiations