Thoreau

The objections which have been brought against a standing army, and they are many and weighty, and deserve to prevail, may also at last be brought against a standing government. The standing army is only an arm of the standing government. The government itself, which is only the mode which the people have chosen to execute their will, is equally liable to be abused and perverted before the people can act through it.

The meaning that i think this pasage is trying to say is that the people chose the government for the country but the government is the one who rules us. We the people will fail before the government fail itslef. The army works for the country but is not a part of the government. The army is a part of the government but the government controls them aswell.