Sentence:  Our country has come through a painful period of trial and <WSD>disillusionment</WSD> since the victory of 1945. We anticipated a world of peace and cooperation. The calculated pressures of aggressive communism have forced us, instead, to live in a world of turmoil. 
Meaning of the word marked with <WSD> tags:  A feeling of disappointment, akin to depression, arising from the realization that something is not what it was expected or believed to be, possibly accompanied by philosophical angst from having one's beliefs challenged.