noun. In fortification, the art or act of throwing up fortifications about a place, either for defense or attack; the line of works so formed.

noun. The act of surrounding with a wall or rampart.

noun. A line of field works made around a besieged place and the besieging army, to protect the camp of the besiegers against the attack of an enemy from without.

noun. A rampart or other defensive entrenchment.

"The Green Mountain warrior suggested that the besiegers should be protected by what is termed circumvallation -- that is, by a line or series of works surrounding the place, not to serve offensively against the place, but to defend the siege army from an attack from without."

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