Complex sentence: The expressions have been used as a catchword for the assertion that Communism is a Jewish conspiracy, and it has often coincided with overtly aggressive nationalistic tendencies in the 20th century and 21st century.
Split into simpler sentences: The expressions have been used as a catchword for the assertion that Communism is a Jewish conspiracy. It has often coincided with overtly aggressive nationalistic tendencies in the 20th century and 21st century.