He undertook to keep it there and destroy it on the spot, instead of having to pursue it everywhere without ever being sure of getting at it.

He had at his disposal eleven legions, about fifty thousand strong, and five or six thousand cavalry, of which two thousand were Germans.

He placed them round about Alesia and the Gallic camp, caused to be dug a circuit of deep ditches, some filled with water, others bristling with palisades and snares, and added, from interval to interval, twenty-three little forts, occupied or guarded night and day by detachments.

The result was a line of investment about ten miles in extent.

To the rear of the Roman camp, and for defence against attacks from without, Caesar caused to be dug similar intrenchments, which formed a line of circumvallation of about thirteen miles.