Complex sentence: It is easy to see that "the Connies" is allegory for "the Commies", an abbreviation of "Communists", given that the book was written during the Cold War and the Korean War.
Split into simpler sentences: It is easy to see that "the Connies" is allegory for "the Commies", a term for Communists. The book reflects the times, written during the Cold War and the Korean War.