Mortars and shells wanted at the front: Importance of horizontal fires at Petersburg

We often read the Petersburg siege demonstrated the emergence of “modern war” in some fashion.  The “coffee table book” history draws the the comparison between Virginia trenches of 1864-5 to French trenches of 1915-8.  There is some resemblance, but no more than any functional nature would derive.  Men can only dig a hole in the ground for protection in a finite number of combinations.  Nice surface comparison, but for the most part the trenches are not exactly a mountain of evidence for the “modern war” argument.

If looking to draw positive connections between Petersburg and the tactical nature of warfare in 1915-18, there are two aspects I suggest we examine – the increased use of vertical fires and  changed operational tempo.  That latter point – what we call OPTEMPO in modern parlance – I’ll save for a later post.  But I have mentioned vertical fires earlier this year in relation to the Overland Campaign… particularly Cold Harbor.  And of course, mortars were heavily employed to support the assault after the mine went off.  In the late summer of 1864, the mortars took on added importance at Petersburg. A series of correspondence on August 14, 1864 demonstrates this. That morning, Brigadier-General Henry Hunt wrote to his capable subordinate, Colonel Henry L. Abbot in charge of the siege artillery, directing mortars to the front:

Four 10-inch mortars with a proper supply of ammunition are wanted in the battery near the Taylor house to control a battery of 32-pounder rifles just beyond the crest, distance from 1,200 to 1,500 yards. It would be well to get them out to-day ready to move; they may be ordered into battery to-night. I will inform you then whether to send them. Please answer.

Hunt’s request was to meet a specific tactical need – silencing a Confederate battery that occupied a particularly troublesome position.  The answer to this problem was not direct, or horizontal fire.  Rather he proposed using heavy mortars to fire indirectly, or vertically, onto the Confederate position.  Abbot answered almost immediately that morning and set in motion actions to place the mortars that night. Abbot later suggested a specific position for the mortars, based on earlier experience along that line:

If the 10-inch mortars are ordered forward, I would earnestly request that they be put in the fourteen-gun battery where Pratt’s 4½-inch guns were. The range is essentially the same. The approach to this battery is very good, and to the old battery very bad, a matter of great importance in supplying 10-inch ammunition on account of its great weight; and, moreover, this battery is well made and the old battery very ill constructed, constantly caving under mortar fire.

 Looking back at Hunt’s map illustrating the artillery support during the Battle of the Crater, Pratt’s battery is indicated by the number “24” and circled in blue below:


The correspondence does not specify which Confederate battery was the target.  For the map above, I’ve highlighted one such battery, which would be “beyond the crest” and approximately 1,500 yards distant.  Notice the close proximity to the mine crater. The range cited was well within the capabilities of field pieces. The Confederate guns mentioned were indeed large caliber weapons.  But the Federals might have concentrated the fires of several batteries to damage the battery.  However, having read about the thousands of shells dumped on Fort Sumter, we must ask how long and at what cost would that be completed? 

There is no mention if Hunt required the use of 10-inch case shot from the mortars, as used during the Battle of the Crater.  That particular projectile, of experimental nature, would have done well to silence the Confederate battery while field pieces demolished the earthworks protecting the guns with direct fire. 

Concurrent with the correspondence with Hunt, Abbot also opened a request for more mortar ammunition… and not just a routine request… to Captain Theodore Edson, Ordnance Officer at Fort Monroe:

I am out of my supply of Coehorn mortar shells and the rebels are taking advantage of it. Please send me any shells and wooden plugs which you can possibly procure, on the mail boat, telegraphing me when they start. I don’t care for prepared ammunition. Time is very important.

Backig this up, Abbot further explained the pressing need for mortar ammunition to Brigadier-General George Ramsay, Army Chief of Ordnance in Washington and indicted this was a long standing request:

I have sixteen Coehorn mortars in position and not a shell in depot for them. The rebels keep up a constant mortar fire on us. I don’t care for prepared ammunition; all I want are shells, fuse-plugs, and paper fuses. These must be received very shortly or the army will suffer. I wrote on 15th ultimo, and telegraphed on 19th ultimo and 11th instant for a large supply. Please inform me at once whether I am to be supplied. Please also send 2,000 Parrott time-fuse plugs for siege guns.

The Confederates had also learned the value of vertical fire, and were now in position to employ some of the heavy mortars from Richmond along with some expedient weapons.  And at the same time, the Confederates were commencing production of their own Coehorn mortars.

Fast forward to 1917. When preparing the American Expeditionary Force for combat in France, American officers found themselves short of artillery in general.  But most acutely they called for howitzers and mortars capable of high angle fires.  Henry Abbot would have given them an “I told you!” look.  Vertical fires would become the dominant form of artillery support on the battlefield.

(Citations from OR, Series I, Volume 42, Part II, Serial 88, pages 182-3.)