Final answer:
The Soviet Union objected to the peace treaty due to their disagreement with the presence of foreign armed forces in Japan.
Step-by-step explanation:
The Soviet Union refused to sign the peace treaty between Japan and the Allied Powers because it did not agree to withdraw its forces from Japan. The provision in the treaty allowed for the stationing or retention of foreign armed forces in Japanese territory under bilateral or multilateral agreements. The Soviet Union's objection was likely due to their disagreement with the presence of foreign armed forces on Japanese soil.
Learn more about Soviet Union's objection to the peace treaty with Japan