its construction until 1832 the fort's name was "Fortress Monroe", and it was sometimes referred to by that name subsequently. Fort Monroe was the first of the third system forts to begin construction, and was intended as a headquarters for the system as well as a fort. It is a bastion fort with an irregular hexagon shape and seven bastions. The southern and longest front is divided in two fronts by a bastion in the middle; the other bastions are at the corners. The fort is surrounded by a moat and covers . At the time it was built, the only land access to the fort's location was via a long, narrow isthmus to the north. A redoubt with a secondary moat was built northeast of the fort to guard against attack from this direction; the redoubt no longer exists, but the water gate for the secondary moat remains. The fort has a continuous barbette tier of cannon emplacements on the roof, but only a partial casemated tier in the fort, mainly on the southwestern and southern fronts. No positions for casemated flank howitzers exist on the northern and northwestern fronts (except two alongside the north sally port); this partial tier is unusual in the third system. The main channel the fort protected was to the southeast; a casemated external battery (also called a "casemated coverface" or "water battery") of forty 42-pounder cannon was built just outside the moat in this area. This increased the number of cannon in this direction compared with casemated guns in the curtain wall from 28 to 40; it was accessed from the main fort via a bridge. As of 2018, only a small part of the external battery's north end remains, along with a salient place-of-arms just north of it with three gun positions. The fort's walls were up to ten feet thick and the moat was eight feet deep. The initial design provided for up to 380 guns and was later expanded to 412 guns, intended for a garrison of 600 troops in peacetime and up to 2,625 troops in wartime. However, the fort was never fully armed. Early 19th century The site of Fort Monroe was first garrisoned in June 1823 by Battery G of the 3rd U.S. Artillery Regiment commanded by Captain Mann P. Lomax. As a young first lieutenant and engineer in the U.S. Army, Robert E. Lee was stationed