George Julian Pratt was born on 6 March 1843 in Alexandria, Virginia, the eldest son of William A. and Evelina Pratt. From 1858 to 1861 he attended the University of Virginia in Charlottesville, where his father was employed as superintendent of the university buildings and grounds. The 1860 Federal census reports William Pratt's real and personal estates as $15,000 and $700, respectively. Three enslaved persons held by the family are enumerated in the 1860 Slave Schedule, one of whom—referred to in a letter of 6 March 1863—may have accompanied the younger Pratt during his military service.

After Lincoln's election Pratt joined the "Sons of Liberty," a student militia company at the University of Virginia. When that unit was dissolved he joined a second student company, which on 20 July 1861 entered Confederate service as Co. G, 2nd Infantry Regiment, Brig. Gen. Henry A. Wise's Legion (alternately known as Co. G, 59th Virginia Infantry). Pratt served in Wise's commands in western Virginia (July-December 1861) and in the Department of Norfolk (January-February 1862). In the latter instance he seems to have been singled out by Wise for special duty, assigned "to enlist and organize a company of marine artillery to defend the marshes at Roanoke Island" (Confederate Veteran, vol. 33 (1925), p. 103). He was captured, with most of the rest of the Confederate defenders, when Roanoke fell to Brig. Gen. Ambrose Burnside (8 February 1862). At some point in 1862—after his parole on 21 February but perhaps before his formal exchange, which seems not to have occurred until September—Pratt joined the 1st Virginia Partisan Rangers, a mixed command of infantry and cavalry raised in the Shenandoah by Col. John D. Imboden. He was active in recruiting a mounted company for the Rangers, and was consequently elected 1st lieutenant (11 December 1862). Later that month this company entered Confederate service as Co. H of the newly formed 18th Virginia Cavalry, with whom Pratt remained for the balance of the war, as 1st lieutenant. From June 1864 he was in command of the company. He was wounded on 19 September 1864, at Third Winchester. After the war, Pratt married Mary E. Brown and settled on a farm ("Walnut Grove") in South River Township, Augusta County, Virginia, where he bred livestock. He died at Waynesboro, Virginia on 25 December 1924.

After the disaster at Roanoke and his return home as a paroled but unexchanged prisoner of war, bound by oath not to bear arms, Pratt must have written Wise, requesting the general's help in obtaining his pay and a formal exchange. Wise's initial response (24 March 1862), through his adjutant, is formulaic. A later response, of 12 June, is quite personal, and was intended for use as a testimonial to be sent to Secretary of War Randolph. Through March and April 1862 Wise himself had been peppering Richmond with letters urging the prompt exchange of the Roanoke prisoners, with an eye to regaining his Legion. Randolph could only reply that the Federals refused to execute the agreement (Sherwood and Weaver, pp. 38-40). Wise's letter of 12 June survives as a copy in Pratt's hand, made, presumably, before sending the original on to Richmond. Wise mentions Pratt's "efforts and partial success in recruiting," alluding, apparently, to Roanoke. He closes by asking Pratt to commend him to an "old & cherished friend" at the university, Prof. William H. McGuffey, best known as creator of the "McGuffey Readers," nineteenth-century America's most popular and widely-used series of educational textbooks. Presumably, Pratt sent his appeal on to the Confederate authorities in Richmond, with Wise's original letter enclosed.

Pratt's letter of 11 December 1862 is a celebratory one, brimming over with the news of his election as 1st lieutenant in John Imboden's 1st Virginia Partisan Rangers (by this time also known as the 62nd Virginia Mounted Infantry). Since their organization the previous spring the Rangers had compiled a distinguished record of service, most notably in Jackson's Valley campaign. As Pratt mentions, the captain of his newly raised company was Imboden's brother Francis, under whom Pratt would serve in Co. H of the 18th Virginia until June 1864. Two of the three subsequent letters written by Pratt date from the following March and April, when the 18th Virginia Cavalry—now part of Brig. Gen. Imboden's "Northwest Brigade" of the Department of Northern Virginia—was stationed at the lower end of the Shenandoah Valley. In February, the regiment had been ordered out of its winter quarters at "Camp Washington," in Highland or Augusta County, Virginia, to reinforce Brig. Gen. William E. "Grumble" Jones's brigade. This combined force was to move against Maj. Gen. Robert H. Milroy's Union division, then occupying Winchester (see Official Records, Series 1, Vol. 51, Part II, p. 677). Pratt wrote on 10 March from the home of a Mr. and Mrs. Helsley (possibly Joseph and Jemima Helsley of Cabin Hill District, Shenandoah County) near Edinburg, 25 miles southwest of Winchester. He was recovering here from "a very violent cold" that he and many others in the regiment had contracted during the campaign. Pratt hints that "Old Jones" is partly to blame for the epidemic, arguing that Jones's request for Imboden's aid led to the regiment's "unnecessary exposure" to winter weather without adequate shelter, rations, and camp equipage. The letter indicates that six companies of the 18th Virginia were on detached service to the north in Hampshire County, West Virginia, leaving only three, including his own, encamped in the Edinburg vicinity. Yet "we three," he writes, "number 50 more than the six which have gone." A 6 March 1863 inspection report for Imboden's brigade confirms that the 18th Virginia's ranks were considerably depleted; of 706 men on the regiment's rolls, only 5 officers and 143 men were present and fit for duty (Official Records, Series 1, Vol. 25, Part II, p. 657).

Pratt's illness had "considerably abated" by the time he wrote his mother again on 9 April 1863, from the 18th Virginia's camp at Crab Bottom, Highland County, Virginia, some 70 miles southwest of Edinburg and not far from the regiment's original winter camp. The long spell of "foul weather . . . has cleared off," he writes, "and today is lovely every thing looks like spring." It seems that Co. H's circumstances improved with the weather. Although he worries that his own horse is overworked and undernourished, Pratt reports that "We are the largest and best mounted company in the Regt." On 20 April, no longer checked by winter shortages, Imboden's and Jones's brigades renewed their offensive, and by mid-May they had cut the Baltimore & Ohio Railroad in northwestern Virginia, in the process capturing several thousand horses and cattle as well as over 500 Union prisoners (see Official Records, Series 1, Vol. 25, Part I, pp. 90-105).

On 14 November 1863, Pratt wrote to his father from the 18th Virginia's camp along Elk Run, in Augusta County, Virginia, having recently returned from an "arduous march of 225 miles" through Bath and Alleghany counties in pursuit of Brig. Gen. William W. Averell's Union expeditionary force. Averell's troops had routed Confederate forces led by Brig. Gen. John Echols and Brig. Gen. Albert G. Jenkins on 6 November at Droop Mountain, West Virginia. On 7 November Imboden, west of Warm Springs, Virginia and finding it too late to assist Echols, turned his brigade south and advanced toward White Sulphur Springs along the Jackson River. At Covington, Virginia on 9 November, elements of the brigade skirmished with two Union squadrons from the 8th West Virginia Mounted Infantry under Maj. Hedgman Slack. While Pratt's boast that Imboden's command had "completely out-Generaled, out-marched and in every respect out-done the yankee raiders" during the campaign is not entirely accurate, there is general agreement between his account of the 9 November skirmish and the after-action reports filed by Gen. Imboden and Maj. Slack. The whole affair "lasted about a half an hour," Pratt writes, "when the 'victorious enemy' fell back and commenced a precipitate retreat." Slack reports that after driving an increasingly stubborn Confederate picket line for 2-3 miles, his command came under artillery fire, at which point they withdrew to rejoin the main Union column on the Warm Springs Road (see Official Records, Series 1, Vol. 29, Part I, p. 517). Imboden's pursuit of the Union raiders continued northward into Highland County until mid-November, when it became clear that Averell's troops were retiring to the vicinity of New Creek, West Virginia, "gone," as Pratt writes, "I hope for the winter" (for Imboden's report, see Official Records, Series 1, Vol. 29, Part I, pp. 547-49).