10-inch Mortar round, 17th century, Fort Nashwaaksis, York Sunbury Historical Society, Fredericton Region Museum, Artefact

FRM Artefact, c17th century 10-inch Mortar round

(Author Photo)

          A heavily corroded British cast iron10-inch mortar round found on the site of Fort St. Joseph may be one of theearliest military artifacts in the collection of the Fredericton RegionMuseum.  The French Fort once stood onthe north side of the Nashwaak River across from the present-day Fort NashwaakHotel.  The artefact was donated to themuseum by LeBaron Bell and recorded in the records on 11 April 1932.

          This mortar round would have beenfired from a smoothbore muzzleloading (SBML) Mortar, with a weight greater than2,000 lbs.  It was discovered on the siteof the British siege of Fort St. Joseph that took place on the banks of theNashwaak River on the Northeast corner of present-day Fredericton, in 1696.

          In the late 1600s, these mortars werein wide-spread use by France and England, and at that time were called“grenades”. English mortar rounds in the late 17th century ranged insize from 6 to 18 inches, with references to these calibres appearing regularly in the various inventories by the Office of Ordnance in London from 1675onwards.  A damaged 18-inch cast iron specimen likely cast in England in 1684 is recorded in the collection of the Tower Armouries in London.[1]

In 1696, the capital of Acadia was Fort Nashwaak (Fort St. Joseph),on the East side of the St. John River, now part of the city of Fredericton. Robineau de Villebon was the Commandant in charge of a fort 200 feet square with four bastions and surrounded by a palisade and ditch.[2]  A New England force led by Colonel JohnHawthorne prepared to attack the fort on 18 October.  

Villebonhad placed lookouts at the river’s mouth and knew what was coming. He had onlyabout 100 soldiers, against Hathorne’s 500, but his defences at the fort werehastily improved. Inpreparation for the British attack, de Villebon built a second palisade aroundthe fort and mounted ten cannon and eight swivel guns on its walls.  He had also sent out word calling up every available Acadian forservice. A message was also sent to Father Simon at Meductic, who had the Maliseet go to the fort to aid in the coming fight with Hawthorne.

It was mid-October when word arrived that Hathorne was only acouple of miles below Jemseg. The British set upcamp and manned a battery across the Nashwaak River, which likely included themortar that would have been used to fired the round now with the museum.  Villebon addressed his men and cries of ”Vive le Roi” echoedthrough the fort. The first attack occurred the next morning, and Villebon kepthis men within the fort rather than having them cross the Nashwaak River underfire from the British forces. This attack was repulsed by cannon fire.[3]

Cannon and musket fire then came from both sides, but Villebon’sguns were better mounted and more effective. The British were unable to make progressthat day and because of the cold, they lit fires at night to keep warm.  The fires attracted a further barrage from thefort and the British soldiers had to extinguish their fires.  Hawthorne’s forces took more of de Villebon’scannon fire from the fort again in the morning. Aftertwo days of ineffective bombardment and suffering the harassment of French andnative skirmishers in the woods, the British withdrew on 20 Oct 1696.[4]  They sailed down river, ending the battle of the Nashwaak.

Fort Nashwaak, built by Commandant de Villebon in 1691-92. From Clarence Webster, Acadia at the End of the 17th Century

In broad terms, a mortar is a piece of artillery designed for indirect fire at very high angles to aim at targetsprotected by walls, trenches or rough terrain. That’s in contrast to regular cannons which are designed mostly for direct fire, with their projectile beingpropelled straight at their target rather than in a curve.

Mortars are first recorded in militaryhistory in the early to mid-15th century in both Korea and the siege of Constantinopleand retained the same basic shape up until the Great War, similar to theapothecary’s thick-walled bowl from which they get their name.

Mortars of that time had a few maincharacteristics. The first one was its projectile, its shell or bomb, a verylarge projectile filled with black powder. It had a cast iron body withhandles/ears for loading and thicker walls at the bottom to resist the initial propelling blast (Fig.4), said blast also being used to light the time fuse(C.) made up of a hollow wooden cone filled with either compressed black powder or slow-burning paper.

Mortar Diagram. (The Napolean Series Archive)

Although less propellant was used proportionally to the weight of the projectile compared to regular cannons -the latter needing large amounts to shoot with a flat trajectory- each shot still required several kilos of black powder to move these massive projectiles, resulting in incredible pressure building up inside the gun. To manage this, mortar barrels are built with extremely thick walls, especially around the propellant chamber on top of which the bomb sits.

The final characteristic of a mortar is its very sturdy baseplate, made first from wood then from cast iron starting in the 19thcentury, made to absorb the recoil of the gun without being crushed against the ground. It also included a wedge and its resting block -the coin demire and coussinet in French- which allowed the gunner to fine-tune the firing angle of the gun, which along with the amount of propellant was used to range it. Most mortars fired between a 45° and 60°angle.

(Author Photo)

French Cast Iron 13-inch Mortar, C, 4338,on the barrel, (Serial No. 22) on the right trunnion, 1, 30-48-cm bore, ca.1758, from the Fortress of Louisbourg, Nova Scotia.  On display in the Canadian War Museum,Ottawa.

These very large guns were almost exclusively used whenattacking or defending fortifications to destroy targets beyond its walls butstarting in the 17th century lighter mortars were used that worked equally wellin the field. The coehorn, named after Dutch military engineer Menno vanCoehoorn, was a light artillery piece that could be carried by two soldiers andused to fire upon entrenched soldiers or large formations. Although the smallerprojectiles did not fragment as well as our modern projectiles, and theirtrajectory could be avoided by any soldier with a keen eye and a bit of luck,it proved very effective at its main purposes of providing cover, suppressivefire and laying waste to enemy trenches. While siege mortars mostly evolvedinto even larger howitzers around the second half of the 19th century, it’sthese smaller coehorns that evolved into modern mortars.[5]

[1] Brian G. Scott, The deploymentof Mortars in Ireland up to the 1689 Siege of Londonderry, Ulster Journalof Archaeology, Vol 73, 2015-2016,

[2] Joseph Robineau de Villebon (22August 1655 – 5 July 1700), was born in New France, but received much ofhis education and military experience in France. He returned to New Franceabout 1681 and deployed to Acadia c1685, where he re-established French rule.  On 7 April 1691, the king appointed him“commandant in Acadia,” aposition he held until his death at Fort Saint-Jean in Acadia. He built the capital at FortNashwaak and was able to maintain the New England-Acadia boundary inpresent-day Maine because of his military talents and his skill in dealing withthe First Nation Wabanaki Confederacy. (Dictionary ofCanadian Biography)

[3] John Wood, blog, The Razing ofChignecto and the Attack on Fort Nashwaak, 5 July 2017.

[4] W.E. (Garry)Campbell, The Road to Canada, The Grand Communications Route from Saint Johnto Québec, (Goose Lane Editionsand the New Brunswick Military Heritage Project, Fredericton, New Brunswick, 2005), pp. 21-23.

[5] https://qsy-complains-a-lot.tumblr.com/post/614034303952748544/what-is-a-mortar/

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