There’s a fine line, I think, when interpreting the July 1863 activity on Morris Island. The simple story is that Brigadier-General Quincy Gillmore’s offensive stalled when direct assault on Battery Wagner failed with heavy casualties, then he turned to long and involved siege operations. Sure, that summarizes the campaign in twenty-five words for a general history of the war. Such leaves the impression that Gillmore planned to overrun the Confederates on Morris Island with a brute force infantry assault. Such an assumption is not supported by a review of Gillmore’s orders or his reports, and that of his subordinates, from July 10, 11, and 12. As mentioned earlier, the assault of July 11 was prompted by reports that the battery was vulnerable (arguably it was) and might fall by direct assault. On the other hand, very apparent is that Gillmore expected to gain Battery Wagner with a short, less-deliberate siege.
After the failed assault on July 11, Gillmore directed counter-batteries established to keep pressure upon Battery Wagner. Gillmore asked Rear-Admiral John Dahlgren to add the weight of his ironclad’s guns to the Army’s batteries. The revised plan read:
It was determined to attempt, with the combined fire of the land batteries and gunboats, to dismount the principle guns of the work, and either drive the enemy from it or open the way to a successful assault.
Short of a formal siege, Gillmore still held to the notion the Confederate works could fall with a dash. But he recognized the need to suppress the defenses before that dash was made.
In his journal of activities, Colonel Edward Serrell, 1st New York Engineers, noted on July 12:
Received orders to begin a line of works against Fort Wagner; to put in six Wiard Guns, four of Brayton’s battery, six Parrott 10-pounders, and five Requa guns; and, in the second line on the left, prepare for ten Parrott 10 and 30 pounders, as they could be obtained, and intersperse with light mortars in the sand-hills, in suitable positions.
Serrell’s engineers also began construction of a line of works, with the 3rd New Hampshire assisting with the labor. That line would become the first parallel in the siege operations against Battery Wagner, some 1,350 yards away. That night, Major Thomas B. Brooks took over some of the duties previously assigned to Serrell. While Serrell focused on positions for the light batteries, Brooks supervised construction of the Parrott batteries on the left. These batteries would provide both direct and high angle fire converging upon Battery Wagner, in conjunction with the Navy’s fires. On the map below from Major Brooks’ report, I’ve overlayed the respective positions of the batteries with the lines of fire.
Green lines indicate direct fire. Yellow indicate high angle mortar fire. Notice the causeway used by the Federals between the “Left Batteries” and the Beacon House.
Between July 12 and 16, the engineers built four main battery positions. Batteries Reynolds and Weed were on the right, close to the shoreline. Using one of Brooks’ maps from the Official Atlas, here’s a close view of the batteries in relation to the parallel:
Note this map depicts fortifications that existed near the end of operations at Morris Island. So I’ve circled the works discussed here. The annotation “B.P.M.” indicates the location of bombproof magazines for the guns. Battery Reynolds was 1,335 yards from Battery Wagner. By July 17, Battery Reynolds contained a mix of field and siege guns:
- Five 8-inch mortars
- Two 30-pdr Parrotts
- Six 10-pdr Parrotts
- Four 3-inch Ordnance Rifles
- Two 3.67-inch Wiard rifles
Battery Weed contained five 10-inch mortars and sat 1,460 yards from its target.
On the left, Batteries Hays and O’Rorke sat offset to the line of advance for any infantry attack on Battery Wagner. Again, here’s the detailed location on the map:
Engineers split Battery Hays into several detached sections. Again, because this map depicts works build later in the siege, I’ve circled the sections used in this phase. Battery Hays included seven 30-pdr Parrotts and four 20-pdr Parrotts. To the rear was Battery O’Rorke with five 10-inch siege mortars, which made use of earlier Confederate attempts to build a battery in that area. Battery Hays and O’Rorke were 1,830 yards and 1,900 yards, respectively, from Battery Wagner.
These works demonstrate Gillmore’s intentions leading up to July 18. The arrangements were not that of a prepared siege as he supervised the previous year at Fort Pulaski. Rather these batteries, totaling 25 rifled pieces and 15 mortars, were more so a hasty effort to silence, not reduce, Battery Wagner.
Since I’ve mentioned Fort Pulaski, let’s compare. During the Fort Pulaski siege, Gillmore made use of weapons up to 10-inch columbiads and 13-inch mortars. In fact the smallest weapon used to fire upon the fort were 30-pdr Parrotts. In the case of the initial bombardment of Battery Wagner, 30-pdr Parrotts were the largest guns used. Likewise, notice the use of one caliber smaller mortars at Battery Wagner. (NOTE… I’m just referring to the batteries employed against Battery Wagner on July 17. As even a casual reader will recall, much heavier weapons appeared on Morris Island later in the siege.)
In terms of ranges, the batteries on Morris Island were closer to the target than those on Tybee Island in April 1862. Such is more so due to the topography of Morris Island than any change in tactics. The siege mortars, however, were working at extreme range for their type. In fact, the 8-inch mortars at Battery Reynolds could barely reach Battery Wagner. At Pulaski, Gillmore relied on heavier 13-inch seacoast mortars for the high angle fires.
But the nature of the target differed on Morris Island. Instead of brick and mortar, Battery Wagner was built of white quartz sand. Gillmore, being an engineer, noted the properties of the beach sand:
The material of which Morris Island is formed, and of which the batteries, trenches, and other siege works were constructed, is a fine and almost white quartz sand, weighing, when dry, 86 pounds to the cubic foot. Twenty-four pounds (about 3 gallons) of water will saturate 1 cubic foot of this sand, which is thereby decreased in volume about 5 per cent. Its power of resisting the penetration of shot is also decreased by wetting, while a steady and gradual accumulation of pressure, like the moving of heavy wheels over it, produces a greater effect, by at least three-fold, upon the dry than upon the wet sand.
Fortifications built of sand were not new to military operations. Manuals of the day included estimates of penetration. But what Gillmore banked on for the actions of July 18 was the effect of fires, not penetration. Could the guns and mortars arrayed against Battery Wagner disable the Confederate guns? The answer to that brings accuracy of fire, weight of shot, and duration of bombardment into the discussion. I’d submit Gillmore’s hasty preparations shorted two of the three.
Two notes in closing. First there is the reference to the Requa batteries. I’ll post more later, as the use of proto-machine guns is in the operation is worthy of more details.
Second, notice the names of the batteries placed on Morris Island – Reynolds, Weed, O’Rorke, and Hays. Any coincidence that word of fighting at Gettysburg was making its way south at this time?
(Citations from OR, Series I, Volume 28, Part I, Serial 46, pages 13, 14, and 227-8.)