The long service history of the American Coehorns

I was about to start a post discussing the service history of the Model 1838 Coehorns. But how easily one is distracted! I started out to outline the post, which led me on a quest for the “end point” of the essay – when the Coehorns left the active inventory. That end point became a good story….

I suspect most are familiar, at a high level at least, with the use of Coehorns in the Civil War. Because of limited numbers on hand early in the war, the Coehorn’s made their most impact on the battlefields from the spring of 1864 onwards. And mostly in the Eastern Theater at that. (The more I think about those stories, the more I would prefer to save those for “sesqui-timed” posts. But we’ll see how this goes.)

But the Coehorn had a long service life after the Civil War. And these little mortars weren’t just sitting aside in some fort, standing still for monthly inventories. Like the light-weight mountain howitzer, the Coehorn found a niche out west where operational considerations and terrain prohibited heavier ordnance. Perhaps the highlight of the mortar’s service in that time period was the Modoc Wars. A Coehorn, specifically registry number 43 from Cyrus Alger, sits on display at Lava Beds National Monument as an example of the type used in that action.

20061011 Lava Beds NM - California (173)

In response to many long unaddressed grievances, in late 1872, “Captain Jack” (or Chief Kintpuash) leading just over fifty warriors and their families took up a defensive position in the lava beds south of Tule Lake on the California-Oregon border. The position was naturally strong, and made stronger as the Modocs posted sentries and built up basic works. Many of the positions had natural overhead cover. This became the “Stronghold”

Captain Jack’s Cave

In the Army’s first “go” at the Lava Beds, on January 17, 1873, Civil War veteran Lt. Col. Frank Wheaton led a force of around 450 men. Wheaton’s command suffered heavily – 35 killed and 25 wounded – and gained nothing. After that bloody repulse, Wheaton suggested that artillery, particularly mortars, were needed to deal with the Modoc Stronghold.

Colonel Alvan Gillem, also a Civil War brevet General, replaced Wheaton. Gillem heeded the suggestion about mortars and brought up two mountain howitzers and four (some say five) Coehorn mortars in March. When negotiations came to a dramatic and bloody end, with the death of General Edward Canby and a peace party on April 11, the Army attacked the Stronghold again, with the mortars playing an important role.

Map of the Stronghold Area

The second battle of the Stronghold started on the night of April 14 and ran through the 17th. The role of the Coehorns was to suppress the Modocs and allow the soldiers to probe for weak spots in the defenses. At night, the Coehorns maintained fire to deny the Modocs any respite. However, because Gillem was unable to seal off the Stronghold, the Modocs were able to escape the position.

In one respect, Gillem had broken the battle of position, but he failed to capture or destroy the Modoc fighting force. The remainder of the War played out over a couple of months, with more fluid combat actions. There was little need for mortars, short of defending the Army’s camps and the captured Stronghold. In June, the new commander on the ground, one Brigadier General Jefferson C. Davis, announced the capture of Captain Jack, who was executed the next month.

I’ll save the finer details of the Modoc War to those who write about the Indian Wars with more authority. But within my focus is how the mortars were used and how effective that use was. Clearly the Coehorns at the Stronghold were not brought up for the breaching role they’d been designed for. These were employed instead within as indirect fire supporting a deliberate assault. The fighting might be described as a primitive “fire and maneuver”, perhaps resembling the fighting seen on some World War II battlefields more so than anything from the Civil War. And at the same time, the Stronghold more closely resembled the Japanese positions on Peleliu than Petersburg. While arguably unsuccessful, the use of Coehorns in the Modoc War does show some adaptations in the years after the Civil War.

Like the Mountain Howitzer, Ordnance Rifle, Napoleon Gun, and Rodman Gun, the lowly Coehorn soldiered on to the end of the 19th century. The Army did develop a replacement for the Coehorn – the 3.6-inch Rifled Mortar Model 1890.

The rifled breech-loader used bagged propellant charges. It weighed at least a hundred pounds more than the Coehorn. The Army bought only 75 of these little mortars. Most were issued to coastal forts where they were used to train gunners, being less expensive to operate than the large caliber 10- and 12-inch seacoast mortars. Some were used in the Spanish-American War. But these were an evolutionary dead end for the mortar. By 1917, in somewhat a technological turn around, the Army scrambled to acquire muzzle-loading, smooth-bore Stokes mortars for use in the trenches of France.

The American 24-pdr Coehorn Mortar Model 1838, itself a close copy of a British design dating back to the 18th century, had an active service life extending through seven decades. There’s something to be said for a sound design.