John Roberson Diamond, businessman, farmer, and Confederate military officer, was born on May 14, 1820, in DeKalb County, Georgia. Sometime near 1840 John married Emiline R. The couple subsequently had ten children: Nancy G. (b. 1841), Frances L. (b. 1842), James L. (b. 1844), Warner N. (b. 1846), William W. (b. 1848), George Ann (b. 1850), Mary I. (b. 1852), John W. (b. 1854), Ely F. (b. 1856), and Amanda O. (b. 1859). By 1850 Diamond and his family had settled in Rusk County, Texas, where he worked as a farmer. By 1860 the Diamond family had moved to Grayson County where he settled west of Whitesboro. John's brother, James J., also settled in Grayson County, and the two became partners in operating a depot of the Butterfield Overland Mail at Diamond's Station.
Diamond was an active Mason and Odd Fellow in Grayson County. He served as secretary of the Mason's Whitesboro Lodge, No. 263 and was a charter member of the Odd Fellows B. F. Christian Lodge, No. 102.
John Diamond was an ardent and outspoken secessionist in Grayson County. Only days after Lincoln's election, on November 23, 1860, he chaired a secessionist public meeting in Whitesboro. Diamond called on a select committee to draw up a resolution that requested Gov. Sam Houston to take steps to ascertain the will of the Texas people with regard to secession. To Diamond and the committee, Lincoln's election and his "emphatic endorsement" of the Republican platform that was "in violent opposition of southern interests, and southern institutions," was proof that Texas should leave the Union. It was out of this secessionist mindset that Diamond decided to enlist for service in the Confederate Army when war finally came.
In April and May 1863 James Bourland began organizing a cavalry regiment of five companies that subsequently became known as Bourland's Border Regiment, Texas Cavalry. At the time of this unit's formation, Diamond was elected to the rank of major. Bourland's Border Regiment was assigned to the Trans-Mississippi Department and given the task of protecting the northern border of Texas, hence the name of the regiment.
In October 1863 Diamond was put in command of the Brush Battalion, a group of men assembled by Henry Boren—a deserter from the Tenth Texas Cavalry Battalion—at the behest of Henry E. McCulloch, who declared that eligible men in North Texas either had to join the army and remain there, leave the country, or be killed. Initially the men of the Brush Battalion were hesitant to serve in Bourland's regiment, because they feared their enlistment was a trick by the commanding officer to hang or shoot them. Bourland's reputation for his role in the Great Hanging at Gainesville, Texas, preceded him. However, after discovering that they would be serving under the command of Diamond, the men of the Brush Battalion were reassured, because he had no direct role in the controversial event.
While in command of the Brush Battalion, Diamond was responsible for hunting deserters in the Forks of North Texas. However, on March 26, 1864, Diamond was dispatched along with two companies of the regiment to Fort Arbuckle in present-day Oklahoma. This assignment embroiled Diamond in numerous controversies that were characteristic of North Texas during and after the Civil War. For example, in the spring of 1864 James M. Luckey, a former constable and town treasurer of Weatherford, was rumored to be planning to lead a group of renegades and deserters to establish communications with Union forces and help facilitate a Federal invasion of East Texas. Bourland was alerted to the scheme by William Quayle. In response, Bourland dispatched 100 men under the command of Diamond to Parker County in order to arrest Luckey and his cohorts.
In the end, only fourteen men were charged with any crime, but Diamond added to that total by arresting militia captains Isaac Ward and Charles Adare. These men had actually been part of Diamond's arresting force but were accused of aiding Luckey's men in escaping. After the arrest of Luckey and his men in Parker County, Bourland turned to purging the troops under his command of Unionist sympathizers and would-be deserters. In April 1864 Diamond reported to Bourland that twenty men in a company of the regiment stationed at Head of Elm had already deserted and that more were sure to follow. Bourland ordered Diamond and a select force loyal to the Confederacy to prevent more desertions. Diamond and his men moved on Head of Elm, surrounded the post, and opened fire on its inhabitants. James L. Clark, a militia captain at Head of Elm, claimed that Diamond's men tied prisoners to nearby trees and shot them numerous times.
In April 1864 McCulloch asked Gen. John B. Magruder for more troops to increase Bourland's command to the size of a regiment. Magruder sent four more companies to Bourland and promoted him to the rank of colonel. On May 13, 1864, Diamond was promoted to the rank of lieutenant colonel. However, due to the deteriorating situation for Texans loyal to the Confederacy (renegades continued to make life miserable) and Bourland's tactics, many men on his staff began to question his command. Diamond led the primary faction that opposed Bourland, but his mutinous attitude towards Bourland did little to mitigate the threat that renegades posed to the security of North Texas or to solve the problem of deserters. Regardless, on February 10, 1865, Diamond assumed de facto command of the regiment but still reported to Bourland, per McCulloch.
In the spring of 1865 more than 100 deserters organized in Wise County in the hopes of escaping to Mexico, California, or Kansas. Troops led by Diamond set out to capture the renegades. On April 3, 1865, Diamond and his men located the renegades' camp and attacked and ran off their horses. Surrounded, the renegades sued for negotiations, but this was broken off when Diamond was captured. He was released only after he assured he would return the horses that his men had run off. Once released, however, Diamond threatened to renew the attack which prompted more than 100 deserters and renegades to surrender.
After the war, Diamond returned to Grayson County where on January 9, 1880, he died. Diamond was buried in the Diamond Family Cemetery in Whitesboro, Grayson County.