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Answer: That soldiers are not treated as individual men by the government, but as disposable weapons
Metaphor: The standing army is only an arm of the standing government.
Explanation: When he says the army is only an arm of the government, it becomes the integrants of the army (the soldiers) an arm (weapon). They are not seen just like individuals and people, but like weapons that the government can use when it wants to.
Hope this helps.
