After graduating from West Point, as a brevet 2nd lieutenant, Gibbon was sent to Mexico during the Mexican War but did not see combat. He served in Florida in the Seminole Wars and later was an instructor at West Point where he wrote The Artillerist's Manual. When the civil war broke out Captain Gibbon was commanding Battery B 4th U. S. Artillery at Camp Floyd, Utah Territory.
John Gibbon, his wife, young children and Battery B left Camp Floyd with elements of the 2nd U. S. Cavalry and the 10th U. S. Infantry on July 27, 1861. The column spent 74 days in route to Ft. Leavenworth, Kansas where they arrived on October 8, 1861. From there Gibbon and Battery B went to Washington. Gibbon was soon appointed chief of artillery for General Irvin McDowell. He spent the winter instructing Battery B and three other volunteer artillery batteries. On May 8, 1862 newly minted Brigadier General John Gibbon assumed command of a brigade of western regiments (2nd, 6th, 7th Wisconsin & 19th Indiana) to which Battery B was attached. He would command this brigade at the September 17, 1862 Battle of Antietam.
When John Gibbon's brigade stepped out around 6:00 a.m. on September 17, 1862, advancing south from the Joseph Poffenberger Farm toward the Confederate forces in line of battle about a half mile to their front Battery B followed. They advanced to a field directly south of the North Woods and then to high ground east of the D. R. Miller Farm all the while firing their 12 pounder bronze guns in support of Gibbon's brigade and the other troops in General Doubleday's Division. Soon the 6 gun battery would move to the west of the Hagerstown Pike south of the D. R. Miller barn. Here, while suffering heavy losses in men and horses, they would help repulse General Stonewall Jackson's troops and assist Gibbon's brigade and others in advancing within a couple hundred yards of the Dunker Church.
Confederate General John Bell Hood's counter attack around 7:00 a.m., forced the Union infantry back to and through the cornfield at Antietam and in some cases to the west side of the Hagerstown Pike where they rallied to support Battery B which was receiving heavy fire from Confederates in the cornfield. While this was going on General Gibbon saw that his prized bronze guns, especially the one on the pike, were in danger of being captured by the Confederates even as they fired rounds of double canister at the foe.
In Recollections of the Civil War John noted: "I happened to look at the gun (in the road) and noticed that the cannoneers had carelessly allowed the elevation screw to run down and every time the piece fired its elevation was increased until the missiles were harmlessly thrown high over the heads of the enemy in its front. I yelled to the gunner to run up the elevation screw, but in the din he could not hear me. I jumped from my horse, rapidly ran up the elevation screw until the muzzle pointed almost into the ground in front and then nodded to the gunner to pull the lanyard. The discharge carried away most of the fence in front of it and produced great destruction in the enemy's ranks."
After assisting with the cannon Gibbon encountered Rufus R. Dawes of the 6th Wisconsin who was rallying his men in a field east of the D. R. Miller house. Dawes commented on this encounter in a letter to Ezra Carmen dated March 4, 1898. In the letter Dawes noted: "General John Gibbon came to me as I was rallying my regiment... and I remember one exact expression he used. His face was black with powder smoke. He had been sighting one of his guns. He said by --- --- --- they shan't have these guns and he marched over by my side when I moved my regiment over to the battery".
To an artilleryman, the cannons in a battery, are like their children. It was a point of honor to never loose a gun to the enemy. So at Antietam, even as he commanded a brigade of infantry, John Gibbon still had an attachment to the guns of Battery B which he commanded at the outset of the civil war and for a number years prior to that. In the full uniform of a brigadier general Steel-Cold John Gibbon stood up to the Confederates in the cornfield and probably in so doing helped save his prized guns from being captured.
