The islands of the Amur river were subject to some border clashes between Soviet and Japanese forces during the Manchukuo period. After the invasion of Manchukuo during World War II, the Soviet Union unilaterally occupied many of the islands along the Amur River and prevented Chinese locals from entering. These islands were the site of several military skirmishes during the 1960s. Most of the disputed islands have been transferred to China. Of the 1,680 islands along the Amur, the agreement now recognizes 902 Chinese islands and 708 Russian islands.