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Case 15: Siege

All these plans and the fortifications they project or record were made in anticipation of an attack on the particular fort or town.  The nature of the potential attack differed according to locale, but for the fortifications designed to resist artillery the greatest likelihood was a siege of the sort that was common in Europe.  Vauban, who enjoyed equal if not greater success in besieging fortresses than in constructing them, maintained that there was no fortress that could not be captured by using his methods. These were based on careful approaches by zigzag trenches or saps, the periodic construction of trenches parallel to the fortress, and the steady bombardment of the target by mortars and cannon.

Sieges in North America were of smaller scale than those in Europe, but a surprising number were conducted, particularly during the French and Indian or Seven Years’ War and the American War for Independence.  The former conflict included at least one major siege in each of six campaigning seasons.

Plans of sieges were drawn after the event to record details for future study.

Lieutenant Therbu, Attaques du Fort William-Henri en Amérique par les troupes françaises aux ordres du Marquis de Montcalm prise de ce fort le 7 Aout 1757 (Mainz, 1792). Colored, copperplate engraving. Map Division, M-1914. Maps 4-N-7.

British-held Fort William Henry on Lake George, New York, threatened French control of Lake Champlain and was therefore besieged in 1757.  The logwork fort was subjected to the basic tactics of siegecraft as the French zigzagged their saps toward the walls and bombarded the fort with artillery. William Henry resisted for a week before surrendering.

Lieutenant Therbu’s plan of the siege was derived from plans drawn in the 1750s.  It was produced for a military atlas that recorded the details of various European and North American sieges for planning and educational purposes.

Lieutenant Therbu, Attaques des Retranchemens Devant le Fort Carillon en Amérique par les anglais commandés par le général Abercrombie contre les français aux ordres du Marquis de Montcalm le 8 Juillet 1758 (Mainz, 1792). Colored, copperplate engraving. Map Division, M-1914. Maps 4-N-7.

When a powerful British army approached French-held Ticonderoga (Carillon) in July 1758, the Marquis de Montcalm knew that his tiny fort could not withstand a siege.  He therefore ordered construction of a log breastwork on high ground at some distance from the fort. Although well equipped with artillery, the British commander chose to order his troops to assault the French position instead of conducting a siege.  The result was a debacle that cost the British 1,950 casualties.

The detailed references to Therbu’s map identify unit positions and events of the battle.  Like his plan of the siege of Fort William Henry, it was published in a military atlas.

Plan of the Siege of York Town in Virginia (London, 1787). Colored, copperplate engraving. Map Division, Stevens no. 147. Maps 6-G-17.

The decisive military action of the American Revolution was a siege.  In the late summer of 1781, a British army under General Charles Cornwallis dug in at the small Virginia tobacco port of York on the York River.  The British began constructing fieldworks as a Franco-American army approached from the north. The allies laid siege to the British position from September 28 to October 19, 1781, when Cornwallis surrendered.

This map was published to illustrate Banastre Tarleton’s history of the war.  Although the French and Americans were attacking field fortifications, they still employed the same techniques—zigzag saps and parallels—that would have been employed against a permanent fortress in Europe or America.