At the beginning of siege operations on May 23, about 162 guns stood on the investment line, most in hastily constructed batteries, and these positions were enlarged, strengthened, and supplemented with additional guns in new batteries at advantageous points. Embrasures in batteries close to the Confederate line were closed against rifle balls with plank shutters or bags of packed cotton. The first parallel was made almost continuous from the right on the river to the left of the 13th Army Corps, and as the approaches moved forward, second and third parallels were opened. Loopholes for sharpshooters were made with sandbags or in timber on the parapet. Sixteen principal approaches were begun and eleven carried close to the Confederate line, with loopholes added for sharpshooters wherever fire could be brought to bear. Nine galleries for mines were started and two mines were fired, both at the head of Logan’s approach. By the end of the siege on July 4, about 220 guns, including all from the navy, were on the investment line. Eighty-nine batteries had been constructed, though about twenty were abandoned and their guns moved to the exterior line or to advanced positions, and the aggregate length of Union trenches reached 12 miles. The Confederate line of defense, 8 miles long, mounted about 130 guns in 67 batteries, with works and connecting curtains loopholed for sharpshooters. Damage done by Union batteries was repaired at night, and although a number of guns were disabled by Union fire, in most cases new guns could not be mounted in their places. Countermines against Union approaches and mines were prepared at nine places and four were fired. Retrenchments were made in rear of some works but were not used because the line of defense was nowhere broken. The defense was largely confined to sharpshooting and was maintained for 47 days without relief for the officers and men in the trenches, and part of the time without sufficient rations. Reported casualties from May 23 to July 4 were for the Union 94 killed, 25 wounded, 119 missing, total 638, with 19 officers killed or mortally wounded; Confederate casualties for that span were not separately reported. Reported casualties from May 18 to July 4 were for the Union 766 killed, 3793 wounded, 276 missing, total 4835, with 107 officers killed or mortally wounded; Confederate casualties, river batteries not included, were 873 killed, 2141 wounded, 158 missing, total 3172, with 83 officers killed or mortally wounded.