Complex sentence: The dispute originated after Japan renounced all claims to the Spratly Islands but did not leave a successor when it ratified the Treaty of San Francisco, which left the islands open for occupation by virtue of "terra nullius".
Split into simpler sentences: The dispute originated after Japan renounced all claims to the Spratly Islands but did not leave a successor when it ratified the Treaty of San Francisco. This left the islands open for occupation by virtue of "terra nullius".