For a persuasive letter, You definitely want to have a claim, supporting reasons, and supporting evidence.
Time, mood, speaker, idea
Please tell me if I'm wrong :)
Frist logical connection between the two is that Manzanar Internment and the Japanese living in West Coast of USA are both Japanese people forced to live in isolation because American government thought that Japanese had invaded Pearl Harbour and they must be looked upon with suspicion.
Secondly,in both the cases ,innocent Japanese may have suffered isolation because"Fear was Stronger than Justice".American government was not ready to listen to Japanese people living in USA whether they were innocent or not.They could be potential spy ,ready and willing to assist Japanese in invasion.
