How did the flashback in Chapter 8 add to the plot (1948)?

In Chapter Eight, the author uses flashback to provide background on Gilbert. In this chapter, we learn that Gilbert trained at a military camp in the United States, and that he initially believed that “America is Paradise” (106). Soon after, however, he learned that Jim Crow laws prevented Black soldiers from leaving the base. He also describes his father, who chose to convert to Christianity from Judaism after serving in World War I. Later, in England, Gilbert watches as white residents stare at Black RAF soldiers, and he is astonished that Gilbert, the English people know nothing of Jamaica. He wonders “if Jamaica was in trouble, is there any [English] major, any general, any sergeant who would have been able to find that dear island?” (118).