John A. Dahlgren

He was assigned to the Washington Navy Yard in 1847. While there, Dahlgren established the U.S. Navy's Ordnance Department; became an ordnance expert; developed a percussion lock; and wrote several books, including The System of Boat Armaments in the United States Navy, Shells and Shell Guns, and Naval Percussion Locks and Primers. Under his command, the U.S. Navy established its own foundry to manufacture new equipment. Its first product was the boat howitzer, designed for use aboard ships and in landings.[1]

Rear Admiral Dahlgren, on board the USS Pawnee, beside a 50-pounder Dahlgren rifle (one of his bottle-shaped cast-iron cannons), c. 1864.

His most famous contribution was the Dahlgren gun, a cast-iron muzzle loading cannon. Dahlgren's meticulous research using gauges to measure pressure differences in the cannon barrel as it was fired resulted in a design that utilized slower-detonating gunpowder and merged characteristics of John Ericsson's experimental 12-inch "Orator" (and Robert Stockton's tragically executed imitation, the "Peacemaker") and the shell-guns adapted by French artillery officer Henri-Joseph Paixhans from their origination in the U.S. Army but named after him.[1][3] Dahlgren wrote:

Paixhans had so far satisfied naval men of the power of shell guns as to obtain their admission on shipboard; but by unduly developing the explosive element, he had sacrificed accuracy and range. ... The difference between the system of Paixhans and my own was simply that Paixhans guns were strictly shell guns, and were not designed for shot, nor for great penetration or accuracy at long ranges. They were, therefore, auxiliary to, or associates of, the shot-guns. This made a mixed armament, was objectionable as such, and never was adopted to any extent in France ... My idea was, to have a gun that should generally throw shells far and accurately, with the capacity to fire solid shot when needed. Also to compose the whole battery entirely of such guns.

The U.S. Navy had equipped several ships with 8-inch Paixhans guns of 63 and 55 cwt. in 1845, and later a 10-inch shell gun of 86 cwt. In 1854, the six Merrimack-class steam frigates were equipped with 9-inch Dahlgren shell guns. By 1852, the Dahlgren gun had become the standard armament of the United States Navy.[1]

The boat howitzer derived from a requirement realized during the Mexican–American War. During that war, naval landing parties were armed with various army ordnance, often too cumbersome for landing boats. Dahlgren first experimented with standard army-issue 12-pounder mountain howitzers before devising his own guns system. The boat howitzers came in four basic types: small, light (or medium), and heavy versions of the 12-pounder and a larger 24-pounder. All conformed to the same basic shape, straight gun tubes with no adorning bands or clefts. Elevation was made via a screw-threaded into the knob at the breech. Instead of traditional trunnions, the guns were attached to the carriage by a loop under the barrel. The Dahlgren system also included mounting carriages that facilitated various employments of the guns. A single-axle metal carriage was designed for shore use. A bed-type carriage was used on small boats, with a rail system to allow the gun to be trained fore, aft, and broadside. A similar mount was offered for shipboard use. The system of boat howitzers was used by the U.S. Navy well into the 1890s, with some examples used for ceremonial purposes into the 20th Century.[1]

Dahlgren during the American Civil War

In 1861, Dahlgren's superior at the Washington Navy Yard resigned to join the Confederate navy. President Abraham Lincoln wanted to name then-Commander Dahlgren to the post of commander of the Washington Navy Yard. By law, however, that position could only be held by an officer with a rank of captain or above. Lincoln successfully persuaded Congress to pass a special act legalizing Dahlgren's appointment to the yard. In July 1862, Dahlgren was promoted to captain and made chief of the Bureau of Ordnance. In February 1863, Dahlgren was promoted to rear admiral[4] and took command of the South Atlantic Blockading Squadron. In 1864, he helped William Tecumseh Sherman secure Savannah, Georgia.[1]

Dahlgren's eldest son Charles Bunker Dahlgren (1839–1912), who had studied steam engineering, joined the U.S. Navy at the start of the Civil War and served with distinction, receiving several promotions and ending as the rank of captain. However, he declined offers to continue in federal service after the war. Among other incidents, Charles Dahlgren commanded the siege battery of 9-inch Dahlgren shell-guns which destroyed the powerful Confederate batteries at the Battle of Vicksburg, and served under his father during the blockade of Charleston.[1]

Another of Dahlgren's sons, Colonel Ulric Dahlgren, was killed on March 2, 1864, in a cavalry raid on Richmond, Virginia, while carrying out an assassination plot against Jefferson Davis and the Confederate Cabinet. The plot became known as the Dahlgren Affair. The admiral was deeply troubled by Ulric's death and role in this event, as well as reports of the disrespectful treatment of the corpse before Richmond spymaster Elizabeth Van Lew secured its proper burial.[1]

His brother William also spied on Confederate purchasing agents in England during the war.[5] However, despite Radical Republican associations, John Dahlgren's younger brother Charles G. Dahlgren (1811–1888), a banker and slave owner, became a Confederate brigadier general, commander of the 3rd Brigade, Army of Mississippi, which he personally recruited and funded, until his troops' integration into the regular Confederate army and removal by Jefferson Davis in 1862.[1]