What does “squad bay” mean?
The kids all slept in a single upstairs room: a squad bay of about a dozen beds where my cousins and I played late into the night until our irritated grandma would frighten us into sleep. [pg. 12] of Hillbilly Elegy by J. D. Vance

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A 'squad bay'  is military jargon/terminology for an area where military recruits sleep. A communal and somewhat noisy area as you have young recruits relaxing and playing around as well as sleeping.

By making reference to 'squad bay' as their sleeping location, the author is comparing these kids in some fashion to inexperienced 'green' troops.