Siege Mortars: A War of 1812 Veteran begats Civil War models

More mortar talk today. Allow me to highlight an artifact that bridges between the War of 1812 and the Civil War. Thus far, my posts on mortars have focused on the seacoast mortars. Although designed for coastal defense, as highlighted in previous entries, the Army and Navy pressed those heavy mortars into use reducing Confederate defenses. But the weapons designed for that role were the “light” or “siege” mortars.

By definition a siege mortar was light enough to fit in a maneuver army’s siege trains, but fired a shell heavy enough to damage fortification walls. The description “light” was relative. Most weapons of this class weighed between 900 and 2,000 pounds, and somewhat heavy compared to field artillery. But the mortar weights rounded nicely with contemporary siege guns and howitzers. And if these big mortars were slow to arrive at the front line, that was fine. After all, the forts were not going anyplace soon.

The American Army’s use of siege mortars dated back to the Revolution. Indeed, one might say independence was secured from the muzzle of these weapons. Several examples are on display at Yorktown today, representing typical weapons used at that time.

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British Siege Mortar at Yorktown

While many of the mortars used during the Revolution were bronze, the British began a transition to iron siege mortars in the 1790s. An example of that type is on display at Fort Monroe’s Casemate Museum.

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British 8-inch Siege Mortar

I must admit being confused over the mix of administrative and functional markings on the piece.

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Trunnion markings on the 8-inch Mortar

But trophy inscriptions leave little doubt as to the weapon’s service life. It was captured by the Americans at Fort George, in May 1813.

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Inscription on the top of the mortar

For our Civil War connection here – what regular army colonel played a critical role in the capture of the fort? Winfield Scott.

The mortar bed provides a bit more of the service history.

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Inscriptions on the mortar bed

Over a year later, the new owners put this mortar to use in the defense of Plattsburgh – a campaign that culminated on September 11, 1814.

But bringing us back to the discussion of Civil War siege mortars, there are a lot of similarities between this British weapon and the later pattern American mortars. The weight stamp, given in hundredweight increments, indicates 938 pounds. That’s no far off the 930 pound regulation weight listed in the 1850 Ordnance Manual for the 8-inch Siege Mortar, Model 1840.

The lower stamp relates performance data. With two pounds of powder, the mortar ranged to a maximum of 2000 yards. The 1851 Instructions for Heavy Artillery indicated the American 8-inch siege mortar in use at that time ranged 1,837 yards with two pounds of powder.

But we could dismiss similarities with those particulars as weapons of the same caliber and class. On the other hand, it’s hard to dismiss the external similarity between the British mortar and the later American patterns:

Model 1840 Siege Mortar Diagram

With no other Civil War era weapon can we so easily trace a British lineage. The siege mortar patterns established in 1840 were for all practical purposes copies of a fifty year old British design. In the next post in this set, I’ll discuss the 8- and 10-inch Siege Mortars of 1840. But for now, I’ll steal dual credit for a War of 1812 Bicentennial post and a Civil War artillery post!