As Circumstances Permitted: Capt. James Duane and his Reconnaissance of Antietam Creek's Crossings on September 16

     Antietam Creek provided a question that George B. McClellan needed to answer. In order to fight the Army of Northern Virginia at Sharpsburg, his army had to navigate across that stream. Doing so presented an issue for the Federals, as straddling a stream in the face of the enemy was a less than ideal situation, something the Union commander experienced in the Seven Days' Campaign. Few officers in the Army of the Potomac were better suited to finding reasonable places to cross the Antietam than Capt. James Duane.

Capt. James Chatham Duane (courtesy
of the United States Lighthouse Society)

     Since his graduation from West Point in 1848, Duane had served in the Corps of Engineers, both in the classroom and in the field. At Antietam, he commanded the Army of the Potomac's Regular Engineer Battalion and served on McClellan's staff.(1)
     The situation on the northern end of the Federal line did not present as much of an issue as the state of affairs in the sector of the Ninth Corps when it came to crossing the Antietam. There, Confederate forces positioned themselves overlooking the creek and a major bridge crossing (the Lower, or Burnside, Bridge). In fact, some of the Confederate skirmishers held a foothold on the creek's eastern bank, making any Federal reconnaissance surveying the approaches to the bridge or additional crossing points incredibly difficult. Despite those circumstances, McClellan looked to Duane and his engineers to survey the creek on the battlefield's southern end.
     In the battle's aftermath, Duane's work on September 16 fell under criticism. Ninth Corps commander Jacob Cox recalled that Duane notified him of only two fords on the battlefield proper that the army could utilize. One was between the Upper and Middle bridges "and another about half a mile below Burnside's bridge, in a deep bend of the stream." While this ford was ultimately used by portions of Isaac Rodman's flanking column, Duane's command missed "another practicable crossing for infantry a short distance above the bridge" and Snavely's Ford, which is about 1.35 miles downstream from the Burnside Bridge crossing, according to Cox.(2) With Duane's pedigree, these missed fords might come as a surprise. In reality, battlefield circumstances prevented Duane and his engineers from ever getting an accurate look at the various crossings in Cox's sector.
     James Duane published the Manual for Engineer Troops in 1862. The manual's first chapter--its first pages even--dealt with an army's passage of a river. The term "river" here applies to the Antietam. "The selection of the place and means of crossing a river, is determined by a reconnaissance," said Duane, "which should be as detailed and extensive as circumstances will permit." In ideal circumstances, one means of discovering a ford is "by sending a number of mounted men across wherever there is a probability of the river being shallow enough." Duane continued: "The most certain method [of discovering a ford] is to float down the stream in a boat, keeping it in the swiftest part of the current, where the stream is usually the deepest. Over the stern a sounding line of the proper length is hung; when this touches bottom the river is sounded across."(3)
     Federal reconnaissances of the lower Antietam on September 16 were not confined to Duane's work. Captain Hiram Devol led Co. A, 36th Ohio Infantry, towards the bridge from the southeast and drove Confederate skirmishers back to the west bank of the creek. Simultaneously, Capt. James Wren and his company of the 48th Pennsylvania Infantry proceeded downstream from the bridge and found nothing of note except enemy cavalry on the opposite bank.(4) Devol's movement cleared Confederate skirmishers from Duane's path but unfortunately for the Federals, Duane's reconnaissance was already wrapped up. Thus, when the engineer tried to find crossing points for the Ninth Corps earlier that day, Confederate skirmishers east of the creek impeded that effort.

This section of the daybreak (September 17) Carman-Cope map shows the Confederate defense of the lower Antietam, including the reestablishment of a picket line east of the Burnside Bridge. While Walker's Division was not present near Snavely's Ford until early on September 17, Confederate infantry and cavalry pickets patrolled the area covered by his division on September 16 while Duane was conducting his examination of the creek.

     Aside from the enemy preventing Duane from gathering the needed intelligence about fords on the lower Antietam, time to conduct reconnaissances as outlined by Duane--those of the mounted and boat variety--was limited as McClellan could not dally all day while awaiting information on crossings of the creek. Regardless, Confederate pickets posted along Antietam Creek made it impossible to send cavalry across to test the creek's depth. Floating a boat down the stream was even more out of the question.
     A lack of understanding of the lower Antietam and its crossing points certainly did no favors for the Ninth Corps on September 17. Duane's reconnaissance of that area was flawed, no doubt, but, under the difficult circumstances, it was impossible to provide the high command of the Ninth Corps with any accurate information about the creek without testing the water's depths in person. Confederate skirmishers prevented Duane from accurately obtaining "the selection of the place and means of crossing a river."

Notes:
1. http://penelope.uchicago.edu/Thayer/E/Gazetteer/Places/America/United_States/Army/USMA/Cullums_Register/1371*.html
2. Cox, Military Reminiscences, vol. 1, 301.
3. Duane, Manual for Engineer Troops, 7-8.
4. Carman (Clemens, ed.), The Maryland Campaign of September 1862, vol. 2 "Antietam," 25; Priest, ed., Captain James Wren's Civil War Diary, 88-89. Carman's recounting of these two actions comes after discussing the afternoon movements of the Ninth Corps as ordered by McClellan, indicating that they occurred later in the day, certainly after Duane's own reconnaissance had concluded. The timing of these moves is further proven by Wren's diary, which states that his, Wren's, movement commenced at about 4 pm.