Sentence:  Fearful of inviting a military showdown with the West which they could not win , the Communists seek to undermine Western power where the nuclear might of the West is irrelevant - in backwoods guerrilla skirmishes , in mob uprisings in the streets , in parliaments , in clandestine meetings of undercover conspirators , at the <WSD>United</WSD> Nations , on the propaganda front , at diplomatic conferences - preferably at the highest level . 
Meaning of the word marked with <WSD> tags:  an organization of independent states formed in 1945 to promote international peace and security