The Circular Trench
During the Phase II excavations in Unit EII, at least two stratigraphically superimposed trenches were encountered (Figure 10). The upper north-south trench had cut across a lower, earlier trench that ran diagonally, but nearly east-west. The upper trench is believed to have been dug during the 1850 Army occupation, while the lower trench was dug and subsequently backfilled earlier, probably remnant of an early acequia completed in I724. In the complicated stratigraphy, a possible third trench is located between the upper and lower trenches. Ivey, who excavated Unit EII, believes the middle trench represents a remnant of a circular trench, exterior to the original compound wall corner, which was part of the fortifications installed before the famous 1836 battle. He suggests, through calculations, that the location of the circular trench lies approximately where it is shown on the Labastida map.
The Defenses of the North Courtyard
Although we have discovered the positions and some dimensions of the defensive ditches through archaeology, we have few indications of the actual detailed plan of the courtyard at the time of the Battle of the Alamo. In fact, because of the leveling of the courtyard sometime after 1836, we do not even know what the ground surface level was in 1836, which means we do not know the actual depths of the trenches. The actual depths are needed in order to calculate such things as the heights of the top of the gun positions and the height of the north wall itself. Future excavations may help in estimating these.
Many of the conclusions concerning the present series of excavations make use of rather specialized terms and concepts drawn from field fortification practices in general use in the eighteenth and nineteenth centuries. In order to aid the reader in following our reasoning, a brief outline of these terms and concepts is provided here. All terms are taken from Wheeler (1898), The Elements of Field Fortifications.
The defensive wall of a fortified position was called the parapet. If the top of the parapet was higher than about 4.5 ft above the natural surface of the ground, a small terrace on which the defenders stood was built on the inside of the parapet. This terrace was called the banquette. If possible, the parapet consisted of