The Naked and the Dead BY Mailer, Norman

The word appears 23 times.

I have yet to read this myself and so cannot provide much context. The wikipedia summary states:
The story takes place on Anopopei, a fictional island somewhere in the South Pacific. American forces are faced with a campaign to drive out the Japanese so that Americans can advance into the Philippines. The novel itself focuses on the experiences of one platoon, overseen by Lieutenant Hearn and General Cummings. Although Mailer does not write about the significance or details of the campaign, it is implied that this platoon, like all platoons in the Army, is simply just obeying orders, uncertain what those orders might be.

This makes me wonder why the word would be used so often - as the armed forces were not integrated at this time.

From the samples I read, it appears that the characters are talking about black mistresses and experiences back home before the war.

Not yet documented.