Monday, April 16, 2012

The Unfavorable Mortar Boats

In the later fall of 1861, Captain (later flag officer) Andrew Foote inherited a squadron in the making. The warships under construction and conversion at yards along the Mississippi and Ohio Rivers were far from the ocean going vessels Foote was accustomed to. In a private letter to Army Quartermaster-General Montgomery Meigs, dated November 20, 1861, Foote confessed is dislike for some of the vessels, but saved special criticism for the mortar boats being fitted out:

I have not, fortunately, committed myself in relation to them, although I have a written order from General Fremont to man, arm, and equip them. I never have thought favorably of these boats, either in construction or as an element of power. Still as they were built, and the mortars (12) built, I concluded to move in the matter and kept you informed, or rather asked your authority to go forward. (ONR, Series I, Volume 22, page 438.)
These river mortar boats, not to be confused with larger schooner mortar boats used by the blue-water navy, that Foote wrote of were little more than rafts. A pair of these boats appear in a wartime photo, tied up alongside the USS Tuscumbia.

The mortar boats were, as Foote indicated, a project begun by General John C. Fremont in the early days of the war. The mortars themselves came from Fort Pitt Foundry in Pittsburgh. These 13-inch Seacoast Mortars, Model 1861 - the Army's latest and heaviest seacoast mortars. The Army Ordnance Department designed the weapon to arm coastal fortifications. The 13-inch mortar fired a 227 pound shells fired to a maximum range of 4600 yards. Unlike standard guns, the mortars fired the shells in a high, arching trajectory to fall on top of the intended target. The army designed these seacoast mortars to drop shells upon an enemy bombardment fleet attacking coastal fortifications.

But with wartime needs along the Mississippi River, Army leaders saw an offensive potential with the mortars. Mortars, they felt, could provide a "stand off" bombardment of river fortifications. This concept gained favor in public opinion outside the military, suggesting less bloody means of opening the river.

Trouble was the eight and a half ton mortars were not very mobile. Normally the Army would move such heavy weapons as part of a siege train. But the swampy bottom lands of the river precluded employment such ponderous formations. Instead Fremont opted to float the mortars into position.

Using a typical flat bottomed barge as a basis, the constructors added a platform of timbers. The platform measured roughly 60 feet by 25 feet. Bulwarks, six to seven feet tall, formed a superstructure on top of the platform. Inside the space formed by the bulwarks was room for the mortar, its bed, and handling equipment. Contemporary drawings show the mortars placed on the center line, but in the photo the mortar sits just to starboard.

With all the mortar and equipment inside the bulwarks, there was no room for crew accommodations or any propulsion system. Tugs moved the mortar boats into position, and provided transportation for the fifteen man crew. Additional boats served as floating magazines and berthing facilities. When firing, the crews stood on the aft end of the mortar boat, or when possible, walked out onto shore, to avoid the overpressure blast when the big weapon fired.

Foote inherited the mortar boats as part of the Mississippi River Squadron. Lacking any practical experience with mortars he turned to the Army for help. Initially Captain Archibald G.A. Constable of the 11th Ohio Independent Artillery served as an adviser. Later the Army sent Captain Henry E. Maynadier, a regular army artillery officer.

Charged with supervising the completion of the mortar boats, Foote faced several delays. The progress of the mortar boats received a high level of visibility. On January 23, 1862 President Abraham Lincoln requested a daily report on the progress. The mortars themselves, being a new pattern, were slow arriving in quantity. Mortar beds were also in limited supply. As the material arrived, Foote complained he lacked another key resource - personnel. The Army eventually provided many of the gunners required. By March Foote had over thirty mortar boats ready for use.

Foote employed the mortar boats at Island No. 10. Later the mortar boats carried the fight to Fort Pillow further downstream. Progress on the river mortar boats paralleled similar outfitting for the blue-water mortar boats. Admiral David Farragut prepared ocean-going mortar schooners to bombard Confederate defenses downriver from New Orleans.

In practice the mortars failed to live up to their promise. Long range indirect fires required coordination to adjust the fall of the projectile onto the target. Although balloons were used at Island No. 10, the mortar shell trajectory was simply too unpredictable for proper fire control. Although impressive to both sides, the mortars offered little practical impact on the Confederate fortifications. Long range, indirect fire support from warships had to wait a few decades for more advanced technology - better guns, projectiles, propellants, and communications.

But those mortar boats provide a fair example of the nature of Army-Navy cooperation, even if at times acrimonious, in the early stages of the war. Both services would put the 13-inch mortars to good use later in the war.

Illustration Credits: Naval Historical Center, Battles and Leaders, Author's personal collection.


  1. Hey Craig:

    Cool post. I would like to see more like this on Dahlgren guns, Parrot and Brooke rifles, etc. Two questions:

    1) Is the "live shot" of the coast mortar taken in Charleston?? I've been there and it looks like "the Battery" area down along the waterfront where they have all the artillery.

    2)I'm still trying to find it, but I thought I read somewhere that when they fired this piece, the recoil drove the scow/barge down into the water to a depth where literally the crew was
    looking up from the bottom of a "hole in the water".

  2. Rob,
    Yes the nice "color" photo is from the Battery at Charleston. That mortar has a very low registry number, so I often speculate if it was at Fort Pulaski, Island No. 10, outside New Orleans, or at Yorktown in the spring of 1861. With that low registry number, it wasn't sitting out the war in some depot!

    I've read some secondary sources that reference the recoil on the rafts, indicating some incredible depression into the water. But I've not seen anything that dramatic described in first hand (crew) accounts. There are some interesting newspaper accounts, and a crew-member's recollection posted at the Lancaster at War blog (

    I do know that navy and army officers complained the rafts were wearing out from firing. Keep in mind that the actual rafts were larger than seen in many drawings or lithographs. The photo at the top provides a better study. Looking at the structure and low freeboard, it seems that the recoil would be absorbed mostly as the upper platform pressed onto the water. That means eventually those planks would give way. Indeed, it appears if the outer planks on the raft at the center of the photo above have broken away.