The Abatis

An Article by Gary Zaboly

     One of the least discussed yet most interesting features of the Alamo’s defense works on March 6, 1836 was the abatis of fallen trees placed before the loopholed palisade wall that sealed the gap between church and low barracks. In 1993, when I was trying to make sense of the earliest known plans of the Alamo as a fort, prior to drawing my version of the compound for Stephen L. Hardin’s Texian Iliad, interpreting this section of the fortifications remained a conundrum for the longest time: something was missing. I stayed with this challenge for a number of nights and days, studying the Mexican plans with a magnifying glass and trying to make sense of it all. The intense, closer visual study paid off: like a light bulb suddenly switching on in my brain, I realized that the solution had been in plain sight all along.
     The two plans of the 1836 Alamo fortifications as drawn by Zapadore Lieutenant Colonel Jose Juan Sanchez-Navarro provided the answer and ended the mystery. In his plan drawn mainly to show the assault made by General Cos’ column on the morning of March 6 (hereafter referred to as the “battle” plan), Navarro notes, for the area of the stockade (marked “D” on the plan), and according to one translation: 
      “This was the weakest part of the fort. It was protected [”defendida”] only by a low palisade and a poor barrier of trees. At this place a few colonists tried in vain to escape when they saw all was lost.” [Navarro: 73]
     What he is describing is clear: a row of low, stockaded posts and, in front of it, “a poor barrier of trees.” In Navarro’s other compound plan, seen in his Vista y plano del Fuerte del Alamo (included as a small side insert in an 1840 map of southern Coahuila), the position is described in less detailed terms: “From this point some colonists attempted to escape.” Yet in both of his drawn plans what Navarro shows is unmistakable: a line of round posts for the “palisade” and a scraggly cross-hatching for the “poor barrier of trees,” or abatis.

An earthen redoubt protected by abatis, detail of a much larger canvas by Louis Van Blarenberghe depicting the 1781 surrender at Yorktown.

     A cursory or untrained glance at either plan, or studying poor reproductions of same, does not immediately reveal this. The viewer, in fact, must understand something about military fortifications of the eighteenth and nineteenth centuries to see it. But without a doubt the abatis as drawn by Navarro in both plans is not a ditch. When Navarro draws ditches, they are deliberately rendered quite differently. In his “battle” plan, ditches are shown as straight or curving black lines edged on one side by dots. In his other compound layout, in the “View and plan” (Vista y plano), the ditches are drawn as two straight lines shaded in-between with gray. There is really no confusion of interpretation between the scraggily-sketched abatis and the carefully linear ditches as Navarro drew them.   

     Constructing a barrier of fallen trees to discourage an enemy attack is a very old practice. Early French, Spanish and English explorers in the New World—even the Pilgrims during their 1620 landfalls—often protected their inland campsites with surrounding barricades of brush or cut-down trees. It was a cheap, relatively fast way of creating an outer defense work, and Travis’ Alamo garrison would have been deemed incredibly inept had it not covered the low, vulnerable stockade with such a “barrier”—although the likelihood is that Mexican engineers had placed it there during Austin’s siege of General Cos’ force in 1835.
     The Mexican army was not unfamiliar with such sensible if makeshift defense works built of available natural materials. In describing his march with the Colonel James Grant contingent of the Matamoros expedition in January 1836, R. R. Brown wrote that, some 60 miles south of San Patricio, they came upon a Mexican encampment: “The tents were enclosed around by brush thrown up, and guarded by a sentinel” [Johnson: 422].
     At San Jacinto, a careless Santa Anna ordered the erection, in the words of Colonel Pedro Delgado, of a breastwork…”for the cannon…constructed with pack saddles, sacks of hard bread, baggage, &c. A “rifling”barricade of branches ran along its front and right.” [Delgado:44]
     In other words, an easily knocked-down “breastwork” covered by an incomplete and “trifling”
abatis. A more ambitious abatis at San Jacinto might have dealt Houston’s army a higher rate of casualties, if not stopped its attack. Santa Anna and his officers could not have been ignorant of some earlier disastrous attempts by armies to claw their way through formidable abatis. At the Battle of Assietta in 1748, nearly 5,000 French troops were killed or wounded in a vain onslaught through an unyielding Austrian abatis. In 1758, some 2,000 British regulars and American provincial troops fell in their brave but hopeless charge through General Montcalm’s abatis outside the walls of Fort Carillon, at Ticonderoga. (For a comparison of Navarro’s sketched abatis with the abatis drawn on a plan of the 1758 battle, and how they almost precisely match one another, see the accompanying diagrams).

     Indeed, Santa Anna’s soldiers seemed to have entirely avoided frontally attacking the Alamo’s abatis during their morning assault of March 6, 1836, even if the ditch between palisade and abatis had not been finished [Huffines, Zaboly: 143]. There is no direct evidence of just when the palisade and its “barrier of trees” were erected, but some indirect documentation is available. Texian Samuel Maverick, held in San Antonio de Bexar as a prisoner of Cos in the fall of 1835, remarked in his diary entry of October 17 of the progress of the Mexican engineers:
 ”Timbers &c. taken to El Alamo to fortify the quartel, & begin, on 13th, to blockade the streets, which is finished by the 17th.” [Maverick: 111].
     On November 3 he wrote:
 ”The quartel in the Alamo is very strongly fortified, and the streets to the plaza here well guarded; and all trees, grass, fences and other lurking places and barricades removed and being removed in order to see the Americans when they come up.” [Maverick: 112].
     So it is easy to assume that many of the  “trees” that had been removed from the garrison’s line of cannon and musket fire could have been carried back and arranged in front of the palisade to serve as an abatis.
     In the Mexican War, Santa Anna’s engineers continued to erect abatis as outerworks. At Resaca de la Palma in 1846, Lieutenant Ulysses S. Grant observed that the Mexican army had formed lines on the opposite bank of the river. As he would recall in his Personal Memoirs,
 This position they had strengthened a little by throwing up dead trees and brush in their front, and by placing artillery to cover the approaches and open places [Grant: 62].
     In 1846 General Stephen Watts Kearney encountered a Mexican abatis at Apache Canyon; fortunately for Kearney, its defenders abandoned the position upon his approach. At Cerro Gordo in 1847 the American troops faced a well positioned abatis but, after a tough fight, managed to triumph.
     For much of the remainder of the nineteenth century, abatis continued to serve as defense works in North America and elsewhere. Outside Confederate Fort Donelson in 1862, for instance, U. S. Grant again encountered an abatis: the trees outside of the rifle-pits had been cut down for a considerable way out, and had been felled so that their tops lay outwards from the entrenchments. The limbs had been trimmed and pointed, and formed an abatis in front of the greater part of the line [Grant: 175].
     There are numerous other accounts of abatis built during the Civil War, and a number of photographs of them were taken. (See for example, the abatis outside of earthen-walled Union Fort Slemmer, in Clark: 144-145). One book consulted by officers of this war was Henry Lee Scott’s Military Dictionary (1861), which describes an abatis as: rows of felled trees deprived of their smaller branches, the remainder sharpened to a point, and employed for defence…if branches are properly placed, and intertwined one within another, their disengagement is extremely difficult. An abatis will always be found a very useful and effective auxiliary to the defence of houses or isolated posts, if judiciously placed within range of musketry [Scott: 9-10].                                                         

     In the Sudan wars of 1881-1898, zaribas—improvised barricades of thorny brush and other available vegetation—were used to protect both British and native troops. Twentieth century barbed wire and minefields would largely replace the abatis as effective outer defense works, but wherever vegetation is thick, barriers of fallen trees remain the cheapest and most convenient ways to hinder the approach of enemy infantry.
     In summary, the abatis set up before the Alamo’s palisade wall, most likely by Cos’ troops and perhaps improved by Travis’ men, proved, as Henry Lee Scott noted, “a very useful and effective auxiliary” of the fort’s defenses. It converted one of the weakest points of the Alamo’s fortifications into one of its most inaccessible positions.