Quartermaster General's Office
Washington City, May 13, 1863
Maj. Gen. D. Butterfield,
Chief of Staff, Army of the Potomac:
My Dear General: I send you another copy of the circular of January 2, 1862, in regard to flying columns of troops. It is reported that the Army of the Potomac has just made a movement of eight days duration, carrying with it all necessary supplies, and yet with no baggage trains. If this be literally true, it has changed the whole character of the war on our side, and has done much for our cause. For the benefit of the service, I desire to have all the information I can collect upon the details of the outfit and equipments and the actual performance of the troops on this march.
I will be obliged to your for copies of any orders issued by the headquarters describing the equipments and arrangements for the march, and any observations upon the actual performance of the men. How much and what did they carry? What did they throw away? Were they well fed to the end of the movement?
Yours, truly and respectfully,
M.C. Meigs,
Quartermaster General
In early May, 1863, the new commander of the Army of the Potomac, Major General Joseph Hooker, set into motion a daring plan. He would outflank Lee’s Army, then at Fredericksburg, crossing the Rappahanock behind them, and move on Richmond before the Rebels could maneuver to block him. But the plan did not develop has he hoped, and the resulting Battle of Chancellorsville left Hooker retreating back across the river, having lost around 14,000 men killed, wounded, or captured.
The battles of 1862 had seen the Union armies in the east outmaneuvered and out-marched on several occasions. In March, 1863, General Hooker ordered a commission of officers to investigate how the army might improve their ability to march without the impediment of hundreds of supply wagons. Basing their suggestions on a French model for “flying columns”, the board suggested that the army require the soldier to carry eight days rations at the start of the campaign. Three days worth would be carried in the haversack as normal, the other five placed in the knapsack in the form of 100 hardtack crackers, with meat coming from cattle brought along with the column. By limiting the amount of extra clothing the soldiers would carry, the board believed the overall burden of each soldier would not be noticeably increased. Further supplies would be carried not by the usual wagons, but by trains of pack mules, with two additional mules for baggage assigned to each regiment. It was an ambitious experiment, cut short by the defeat and retreat of the army only a few days into the campaign. A few weeks after the battle, the Chief Quartermaster of the Army of the Potomac, Brig. Gen. Rufus Ingalls, and his subordinates, began to assess the performance of the new system in order to answer Quartermaster General Meigs' questions.
The board of officers had estimated each soldier would carry just over 13 pounds in the now ration-loaded knapsack, which they calculated was more than two pounds less than the usual average. After experimentation, they concluded that "the men, by dispensing with extra clothing, except on extra shirt, drawers, and socks, can carry in their knapsacks one hundred biscuits and eight days small stores." But not all units would properly enforce the strict limit on clothing called for by the board. Ingalls noted in many cases "both blanket and overcoat were carried, but it was not the intention.” The result was that many soldiers were loaded with more weight than the board had imagined.
The 1st Corps reported the each man carried "one change of underclothing, one blanket, one overcoat, in some cases one extra pair of shoes, one piece of shelter tent." In the 3rd Corps the load was the same, except that most apparently did not carry a blanket.
It was apparent to all after the battle that large amounts of equipment had been lost, and not just due to the heavy casualties. Ingalls wrote that already on the second and third days of the campaign many men discarded their blankets and overcoats, and losses in knapsacks were even greater. He estimated that fully one quarter of the army’s knapsacks were lost during the brief campaign, and that figure does not even account for those lost by casualty. The 6th Corps reported more than half lost. The 5th Corps alone lost more than 5,300 (which includes those of casualties). The routed 11th Corps unsurprising lost the greatest number, more than 6,000. Lee’s Chief of Ordnance, Lt. Col. Briscoe Baldwin, reported 11,500 Union knapsacks had been turned in to his department, and noted that many items of equipment were picked up and used by soldiers without being reported. The actual number falling into to Confederate hands was surely higher. It was a large and expensive enough loss that attitudes began to change regarding the wisdom of unslinging knapsacks on going into battle. The 3rd Corps quartermaster opined that there was "often no necessity for it. The result is, that when the line is driven back, or if it is shifted, or if it actually advances, the knapsacks are never recovered, or, if recovered, are found to be plundered." Such losses had to be replaced as quickly as possible at the expense of the Government.
Major problems had also been experienced with the new mule trains. The Quartermaster of the First Corps reported, “The mules used for packing ammunition have suffered very much, from the fact that the men in whose charge they were have not the requisite amount of experience in such matters, and also from the fact that the mules were unavoidably kept saddled and packed for a long time continuously, in momentary expectation of moving.”
The 11th Corps reported that "the ordnance officers in charge were utterly regardless of there animals, and neglected to have their trains watered, fed, or unpacked." These men "used their trains without any judgement or mercy." Even setting aside those guilty of such neglect, one can imagine the effect of placing large numbers of stubborn mules in the charge of men with having little experience with the animal. Based on the amount of damage done to the mules in only a few days time, it's possible a campaign of weeks might have caused such attrition among the animals as to render the trains inoperative.
The mule system had also apparently caused some the of same traffic issues it was intended to avoid. The Cavalry Corps quartermaster wrote to Ingalls, “The delays with a large pack train are very numerous. The train is constantly being disarranged, and interferes in no small degree with the marching of the troops.” Ingalls elected not to repeat the large scale use of pack mules. “The pack-mule system cannot be relied on for long marches with heavy columns. I shall have few hereafter, and intend to make them auxiliary simply to wagons, for short distances over rough country, where there are few and bad roads.”
Hooker’s desire to outmarch Lee to Richmond had caused the army to adopt a new and very different system of supply in short order and without previous practice. Given time, the new system might have been made to work, though it is doubtful how much better it would have proved in the long run than the old system. Ingalls seems to have considered this, and decided the changes were ultimately not worth the effort, and only created new sets of problems. When the army marched north for Pennsylvania in June, there would be no days of rations in their knapsacks, and no teams of pack mules trailing every regiment.

Captioned "I've got enough of Chancellorsville", Alfred Waud sketched one retreating soldier who seems to have commandeered one of the pack mules as his personal baggage transport. (Library of Congress)
Source:
United States War Department. The War of the Rebellion: A Compilation of the Official Records of the Union and Confederate
Armies. Washington D.C.: Government Printing Office, 1880-1901: Volume 25, Part 2 486-562. Making of America.
Web. 4 May 2011.