Salients, re-entrants and pockets
At the Battle of Spotsylvania during the American Civil War, Confederate forces constructed a timber-reinforced line of trenches. The trench line bulged forward to protect a piece of high ground. This curve became known as the Mule Shoe Salient. Union troops concentrated their attack on this point. After 22 hours of hand-to-hand fighting they broke through. The Confederates pulled back to a new position.