"We were armed and drilled as infantry, and in campaigns served as infantry unless there were military bridges or other works to construct. In sieges we served as sappers and miners."
- Lieutenant Colonel W.W. Blackford, C.S.A.

Engineers on both sides of the line at Petersburg designed trenches and defenses that were constructed by infantry soldiers. Field fortifications were used extensively at Petersburg during the Civil War, where miles of competing earthworks zigzagged through the fields around the city. In addition to the construction of fortifications, mining operations also took place behind the opposing trench lines, specifically at the Battle of the Crater.