During the middle of 1863, the unit, as Ruffner's Missouri Battery, was part of a force sent to the Mississippi River under the command of Colonel John Bullock Clark Jr., with the intent of harassing Union shipping.

In early 1864, it became part of Brigadier General Mosby M. Parsons's division, which was ordered into Louisiana in April to counter a Union thrust up the Red River.

While Parsons's infantry fought at the Battle of Pleasant Hill on April 9, Ruffner's Battery served in a reserve role and was not engaged.

The Union troops present at Pleasant Hill continued to retreat back down the river, so Parsons was returned to Arkansas to move against Steele's Camden expedition.

The Governor of Missouri, Claiborne Fox Jackson, mobilized pro-secession state militia, which encamped near St. Louis, where a federal arsenal was located.

Brigadier General Nathaniel Lyon of the Union Army, commander of the arsenal, dispersed the militiamen on May 10, in the Camp Jackson affair.

In response, Jackson formed the pro-secession Missouri State Guard, a militia unit; Major General[a] Sterling Price was appointed as its commander on May 12.

In October, Union forces commanded by Major General John C. Frémont concentrated against Price, who retreated southwards to Neosho, where he was joined by Jackson.

On November 3, Jackson and the pro-secession legislators voted to secede and join the Confederate States of America, functioning as a government-in-exile,[4] first from Arkansas and later from Marshall, Texas.

[4] In February 1862, pressure from Brigadier General Samuel R. Curtis's Union Army of the Southwest led Price to abandon Missouri for Arkansas.

In March, Price, McCulloch, and Major General Earl Van Dorn joined forces to form the Army of the West.

[8] Around September 7, while located at Van Buren, Captain Westley[b] F. Roberts formed a field artillery battery that would bear his name.

[10] The battery was armed with horse-drawn cannons in October: two 12-pounder James rifles taken from Union forces at the Battle of Lone Jack and two obsolescent 6-pounder smoothbores.

[10][11][12] Unlike the smoothbores, the captured James rifles had a series of spiral grooves engraved along the inside of the gun barrel, which spun the projectile when it was fired,[12] giving the cannon greater effective range and accuracy.

[19] Confederate artillerymen were hampered by problems with gunpowder and artillery fuze quality, which often resulted in premature detonation of shells, sometimes while still in the cannon.

In June, the battery, as part of a formation commanded by Colonel John Bullock Clark Jr., moved to the area around the Mississippi River with the intent of interfering with Union shipping.

[27] In late July, Clark's force was transferred back to Little Rock, as the city was threatened by the Union Army of Arkansas under Major General Frederick Steele.

[33] Further Confederate cavalry charges failed to carry the makeshift defensive position, and Marmaduke's men withdrew after engaging in some looting.

On April 9, Parsons's division, as part of Taylor's army, engaged the Union force at the Battle of Pleasant Hill, although Ruffner's Battery was in a reserve role and was unengaged.

[16] While Confederate assaults at Pleasant Hill were repulsed, the Union army, commanded by Major General Nathaniel Banks, continued a retreat that had begun several days earlier.

[35] After Pleasant Hill, General Edmund Kirby Smith, who was in overall command of the Confederate forces, moved his men back into Arkansas, where Steele had occupied Camden.

[39] Smith signed surrender terms for the Trans-Mississippi Department on June 2, 1865;[45] the men of the 1st Missouri Field Battery were paroled five days later, while stationed at Alexandria, Louisiana, ending their combat experience.