Final answer:
Zinn's reference to JP Morgan escaping military service is intended to highlight social and economic inequalities during wartime, suggesting that wealth can shield the privileged from the sacrifices that war demands of ordinary people.
Step-by-step explanation:
When Howard Zinn mentions JP Morgan escaping military service, it highlights the disparities between classes during times of conflict.
Zinn is trying to convey the message that wealth and social status could afford individuals a way to avoid the risks and sacrifices asked of the general population.
This serves to underline the criticism that the costs of war are often disproportionately borne by the less affluent, while the more privileged can evade such burdens, sometimes even profiting from the conflicts. The inclusion of this reference suggests a critique of social inequality and the capitalist system that enables such disparities.