My line was more than fifteen miles long, extending from Haines' Bluff to Vicksburg, thence to Warrenton. The line of the enemy was about seven. In addition to this, having an enemy at Canton and Jackson, in our rear, who was being constantly reinforced, we required a second line of defence facing the other way. I had not troops enough under my command to man these. General Halleck appreciated the situation and, without being asked, forwarded reinforcements with all possible dispatch.
The ground about Vicksburg is admirable for defence. On the north it is about two hundred feet above the Mississippi River at the highest point and very much cut up by the washing rains; the ravines were grown up with cane and underbrush, while the sides and tops were covered with a dense forest. Farther south the ground flattens out somewhat, and was in cultivation. But here, too, it was cut up by ravines and small streams. The enemy's line of defence followed the crest of a ridge from the river north of the city eastward, then southerly around to the Jackson road, full three miles back of the city: thence in a southwesterly direction to the river. Deep ravines of the description given lay in front of these defences. As there is a succession of gullies, cut out by rains along the side of the ridge, the line was necessarily very irregular. To follow each of these spurs with intrenchments, so as to command the slopes on either side, would have lengthened their line very much. Generally therefore, or in many places, their line would run from near the head of one gully nearly straight to the head of another, and an outer work triangular in shape, generally open in the rear, was thrown up on the point; with a few men in this outer work they commanded the approaches to the main line completely.
The work to be done, to make our position as strong against the enemy as his was against us, was very great. The problem was also complicated by our wanting our line as near that of the enemy as possible. We had but four engineer officers with us. Captain Prime, of the Engineer Corps, was the chief, and the work at the beginning was mainly directed by him. His health soon gave out, when he was succeeded by Captain Comstock, also of the Engineer Corps. To provide assistants on such a long line 1 directed that all officers who had graduated at West Point, where they had necessarily to study military engineering, should in addition to their other duties assist in the work.
The chief quartermaster and the chief commissary were graduates. The chief commissary, now the Commissary-General of the Army, begged off, however, saying that there was nothing in engineering that he was good for unless he would do for a sap-roller. As soldiers require rations while working in the ditches as well as when marching and fighting, and as we would be sure to lose him if he was used as a sap-roller, I let him off. The general is a large man; weighs two hundred and twenty pounds, and is not tall.
We had no siege guns except six thirty-two pounders, and there were none at the West to draw from. Admiral Porter, however, supplied us with a battery of navy-guns of large calibre, and with these, and the field artillery used in the campaign, the siege began. The first thing to do was to get the artillery in batteries where they would occupy commanding positions; then establish the camps, under cover from the fire of the enemy but as near up as possible: and then construct rifle-pits and covered ways, to connect the entire command by the shortest route. The enemy did not harass us much while we were constructing our batteries. Probably their artillery ammunition was short; and their infantry was kept down by our sharpshooters, who were always on the alert and ready to fire at a head whenever it showed itself above the rebel works.
In no place were our lines more than six hundred yards from the enemy. It was necessary, therefore, to cover our men by something more than the ordinary parapet. To give additional protection sand bags, bullet-proof, were placed along the tops of the parapets far enough apart to make loop-holes for musketry. On top of these, logs were put. By these means the men were enabled to walk about erect when off duty without fear of annoyance from sharpshooters. The enemy used in their defence explosive musket-balls, no doubt thinking that, bursting over our men in the trenches, they would do some execution; but I do not remember a single case where a man was injured by a piece of one of these shells. When they were hit and the ball exploded, the wound was terrible. In these cases a solid ball would have hit as well. Their use is barbarous, because they produce increased suffering without any corresponding advantage to those using them.
The enemy could not resort to our method to protect their men. because we had an inexhaustible supply of ammunition to draw upon and used it freely. Splinters from the timber would have made havoc among the men behind.
There were no mortars with the besiegers, except what the navy had in front of the city; but wooden ones were made by taking logs of the toughest wood that could be found, boring them out for six or twelve pound shells and binding them with strong iron bands. These answered as cochorns, and shells were successfully thrown from them into the trenches of the enemy.
The labor of building the batteries and intrenching was largely done by the pioneers, assisted by negroes who came within our lines and who were paid for their work; but details from the troops had often to be made. The work was pushed forward as rapidly as possible, and when an advanced position was secured and covered from the fire of the enemy the batteries were advanced. By the 30th of June there were two hundred and twenty guns in position, mostly light field- pieces, besides a battery of heavy guns belonging to, manned and commanded by the navy. We were now as strong for defence against the garrison of Vicksburg as they were against us; but I knew that Johnston was in our rear, and was receiving constant reinforcements from the east. He had at this time a larger force than I had had at any time prior to the battle of Champion's Hill.