What term describes a body of troops stationed in a fortified place?

The term that best describes a body of troops stationed in a fortified place is "garrison." A garrison specifically refers to a military post where troops are stationed, often in a fort or fortified location, to provide defense and maintain a readiness to respond to threats. This term emphasizes both the physical location and the soldiers assigned to protect it.

The other terms, such as "congregation," "force," and "society," do not carry the specific military connotation that garrison does. "Congregation" typically refers to a gathering of people, usually for religious purposes, "force" might encompass a broader array of military personnel or units but lacks the specificity of being stationed at a fortified site, and "society" generally refers to a community of individuals. Therefore, using "garrison" conveys the precise meaning needed to describe troops in a defensive and organized military context.