I don’t know what a parapet is used for or a Barbed wit and fire step

A parapet is a protective wall or earth defense along the top of a trench or other place of concealment for troops. And a barbed wire is wire with clusters of short, sharp spikes set at intervals along it, used to make fences or in warfare as an obstruction. Parapets were originally used to defend buildings from military attack. Barbed wire went from being largely defensive to working as a deadly instrument in World War I. On the front, soldiers laid out wire to defend their trenches.

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