Sentence:  He also speaks of Franklin D. Roosevelt 's `` puerile '' assumption that `` if only he ( Stalin ) could be exposed to the persuasive charm of someone like F. D. R. himself , ideological preconceptions would <WSD>melt</WSD> and Russia 's co-operation with the West could be easily arranged '' . 
Meaning of the word marked with <WSD> tags:  become more relaxed, easygoing, or genial