Supply is the function of providing the material needs of military forces. The supply process embraces all stages in the provision and servicing of military material, including those preceding its acquisition by the military—design and development, manufacture, purchase and procurement, storage, distribution, maintenance, repair, salvage, and disposal. (Transportation is, of course, an essential link in this chain.) The whole process can be divided into four phases: (1) the design–development–production process of creating a finished item, (2) the administrative process by which military agencies acquire finished items, (3) the distribution–servicing processes undergone by military material while “in the service,” and (4) the planning–administrative process of balancing supply and demand—that is, the determination of requirements and assets and the planning of production, procurement, and distribution.

Military supply has always had the basic aim of providing military forces the material needed to live (food, water, clothing, shelter, medical supplies), to move (vehicles and transport animals, fuel and forage), to communicate (the whole range of communications equipment), and to fight (weapons, defensive armament and materials, and the expendables of missile power and firepower). In all these categories are items, such as clothing, vehicles, and weapons, that are used repeatedly and therefore need to be replaced only when lost, destroyed, or worn out; and materials, such as food, fuel, and ammunition, that are expended or consumed—that is, used only once—and therefore must be continuously or periodically resupplied. From these characteristics are derived the basic classifications of initial issue, replacement, and resupply. The technical classifications of supply vary among countries and services. The British army, for example, recognizes two broad classes: (1) supplies, which include all the expendables except ammunition, and (2) stores, which include ammunition and military hardware. The U.S. Army in World War II and for many years after used five main classifications: (1) subsistence and forage, (2) equipment and other items regularly issued to organizations and individuals, (3) fuels, (4) equipment and materials of irregular issue such as construction materials, and (5) ammunition. These five classes were subsequently expanded to 10 by designating as separate classes certain large categories, such as vehicles, medical material, repair parts, and sales items, which formerly were considered as subclasses.

Historically, food and forage made up most of the bulk and weight of supply until the 20th century, when, with mechanization and air power, fuel displaced forage and became the principal component of supply. However, the demand for food remains unremitting and undeferrable, the one constant of logistics. A man’s daily ration makes a small package—seven pounds and often much less. But an army of 50,000 may consume in one month as much as 4,500 tons (4.1 million kilograms) of food.

Animals require much more. The standard grain and hay ration in the 19th century was about 25 pounds (11.4 kilograms), and the daily forage of a corps of 10,000 cavalry weighed as much (allowing for remounts) as the food for 60,000 men. Forage requirements tended, moreover, to be self-generating, since the animals needed to transport it also had to be fed. The number of animals accompanying an army varied widely. Napoleon’s ideal, which he himself never attained, was a supply train of only 500 wagons in an army of 40,000; with a corps of 7,000 cavalry, this would amount to about 10,000 animals exclusive of remounts and spare draft animals. Northern armies in the American Civil War commonly numbered half as many animals as soldiers. A force of 50,000 men might thus require more than 300 tons (272,000 kilograms) of forage daily. This was more than twice the weight of gasoline that an equivalent force of three World War II infantry divisions, using motor vehicles exclusively, needed to operate for the same length of time. In the latter case, moreover, fuel requirements diminished markedly when an army was not moving, whereas the premechanized force had to feed its animals whether moving or not. It was the immense forage requirements of premechanized armies, more than any other single factor, that restricted warfare before the 20th century so generally to seasons and climates when animals and men could subsist mainly on the countryside.

In 20th-century warfare the expendables of movement include fuel for rail and water transport as well as for motor vehicles, and also the immense fuel requirements of modern air power. In World War II, without counting transoceanic shipment, fuel made up half the resupply and replacement needs of U.S. forces in Europe. Technologically advanced warfare has, in fact, vastly increased fuel consumption both absolutely and relatively to other supply needs. The continued development of mechanization and air power has increased by one and one-half times the fuel requirements of large-scale conventional military operations typical of World War II. Food, by contrast, is a small and diminishing fraction of the total burden.

Before the 20th century, equipment replacement and ammunition resupply were a relatively small part of an army’s needs. Missile power before the gunpowder era was limited by the difficulty of bringing missiles in quantity to the battlefield. For the first five centuries of the gunpowder era the provision of ammunition was not a major logistic problem. Not until the use of field artillery on a large scale in the late 18th century, and the development of quick-firing shoulder arms in the 19th, did ammunition begin to constitute a substantial part of resupply needs. As late as 1864, in the Atlanta campaign of the American Civil War, the Union army’s average daily ammunition requirements amounted to only one pound (0.45 kilogram) per man, as against three pounds for rations; Confederate forces in that war were reported to expend, on the average, only half a cartridge per man per day.

The great increase in firepower in the 20th century upset the historic ratios. In World War II the average ammunition requirements of Western forces in combat zones were 12 percent of total needs. In the mainly positional Korean War, ammunition expenditures climbed higher, and a late-1980s U.S. Army planning factor rated ammunition requirements as more than one-quarter of total supply. Material replacement needs have also mounted in absolute terms; the great tank battles of World War II and of the Arab-Israeli Wars of 1967 and 1973 involved the destruction of hundreds of tanks within a few days. But as a percentage of total supply, replacement of material losses is a declining factor.

Transportation

Before the development of steam propulsion, armies depended for mobility on the muscles of men and animals and the force of the wind. On land they used men and animals to haul and carry; on water they used oar-driven and sail-propelled vessels. Among these various modes the balance of advantage was often delicate. A force moving by water was vulnerable to storm and enemy attack; navigation was an uncertain art; transports were expensive and of limited capacity. Large expeditions could be undertaken only by wealthy states or seafaring peoples, such as the Scandinavians of the 8th and 9th centuries, who combined the roles of mariner and warrior. Seaborne armies were rarely strong enough to overcome a resolute land-based foe.

On the other hand, armies have usually been able to move faster and with a better chance of avoiding enemy detection by water than by land. Shipment of bulky freight is cheaper and safer by river than by road, and good roads are rare in military history. In the 19th and 20th centuries the revolution in ship design and propulsion made water travel largely independent of wind and weather, permitting the overseas movement and support of larger forces than ever before. After the mid-19th century, however, more and better roads and, above all, railroads began to offset the historic advantages of water transportation to some degree. In the 20th century motor vehicles and more road building extended the conquest of rough terrain. The airplane finally freed military movement, for modest forces and limited cargo, from bondage to earth altogether. Yet the costs of mobility on land—in equipment, materials, and energy—remain high, and large military movements are still confined to narrow ribbons of rail and road, which in many parts of the world are still rare or lacking.

On land the soldier himself has been the basic burden carrier of armies. As a matter of simple economy, he represents large carrying capacity at no extra cost. His equivalent, in an army of 50,000 in the preindustrial era, would be 1,875 wagons drawn by 11,250 horses or mules, which might need additional wagons and animals to haul forage. A difference of only five pounds (2.3 kilograms) in the soldier’s load could add or subtract a requirement for 125 wagons and 750 animals. Since the days of the Roman legion, the soldier has had to carry, on the average, about 55 or 60 pounds (25 or 27 kilograms). The ratio between weapons and other items in the soldier’s load has varied widely, but the modern soldier has relegated most of his food to vehicle transport while still carrying a heavy burden of weapons and ammunition. Since World War II, however, some armies have made drastic reductions in the combat load.

Before the age of mechanization, the soldier’s carrying capacity was usually supplemented by additional carriers and haulers, human and animal. Each had advantages. A team of six horses ate about as much as 30 to 40 men, but the men could carry more on their backs than the horses could haul and considerably more than the horses could carry. Men could negotiate rougher terrain, and they required less care. On the other hand, loads placed on men had to be distributed in small packages, and men proved less efficient than animals when teamed to haul heavy and bulky loads. The horse and mule, however, have less strength and stamina, though more agility, than the ox, history’s primary beast of burden. In many parts of the world, motor transport still has not displaced human and animal carriers and haulers in the movement of military supply.

Facilities

The provision of military facilities, as distinct from fortification, did not become a large and complex sphere of logistic activity until the transformation of warfare in the industrial era. In that transformation the traditional function of providing nightly lodgings or winter quarters for the troops dwindled to relative insignificance in the mushrooming infrastructure of fixed and temporary installations that became part of the military establishments of the major powers. Modern armies, navies, and air forces own and operate factories, arsenals, laboratories, power plants, railroads, shipyards, airports, warehouses, supermarkets, office buildings, hotels, hospitals, homes for the aged, schools, colleges, and many other types of structures used by advanced societies in the 20th century—as well as barracks, the original military facility. They are among the world’s great landowners. The management of all this improved real estate is one of the largest areas of modern logistic administration.

Services

Services may be defined as activities designed to enable personnel or material to perform more effectively. Usage recognizes no clear distinction between logistic and nonlogistic services, but a somewhat blurred one has grown out of the traditional and opprobrious identification of logistics with noncombat rear-area activities. Thus, intelligence and communications personnel and combat engineers in the U.S. Army have long claimed the label of “combat support” as distinct from the “service support” functions of supply, transportation, hospitalization and evacuation, military justice and discipline, custody of prisoners of war, civil affairs, personnel administration, and nontactical construction (performed by “construction” engineers). Training of combat troops is hardly ever considered a logistic service, whereas training of service troops sometimes is. Usage does not, however, always assign “service support” to logistics. Personnel administration is an old, institutionalized sector of the military establishment, and personnel administrators tend to reject the logistics label. Personnel services (medical, spiritual, educational, financial) are more heterogeneous and have varied origins; most definitions of logistics include them.

Most service activities, logistic and nonlogistic, are of recent origin and, as organized specialities, are peculiar to the military establishments of advanced nations. Over the long haul of military history, the services considered necessary to keep armed forces in fighting trim were generally of a rudimentary character. From the earliest times, however, they posed a serious logistic problem. To armies and their lines of communication they added numbers of people who did not, as a primary function, belong to the fighting force and who, if not properly organized, might weaken its capacity to fight. Soldiers seldom possessed the technical skills required to perform any but the simplest services; sometimes, as members of a warrior elite, they were prohibited by social prerogative from performing them. A classic feature of armies, consequently, has been its long train of noncombatants, often far outnumbering the fighting men.

Logistic services also added to the baggage of armies a growing burden of specialized equipment, tools, and materials needed for the performance of the services. Services tended to generate more services: service equipment itself had to be serviced, sometimes by additional technicians, and service personnel themselves required services. Logistic services thus meant more people to be fed, clothed, and sheltered and more people and baggage to be transported. What the British call the “administrative tail” is as old as military history.