[This article was first published in Army Sustainment Professional Bulletin, which was then called Army Logistician, volume 2, number 3 (May–June 1970), pages 4–7, 28–30.
The text is reproduced as faithfully as possible. To view figures and charts, refer to the issue itself, available on DVIDS and the bulletin’s archives at asu.army.mil/alog/.]
ON THE FIELD OF BATTLE, victory belongs to the nation that can produce and deliver required combat consumables and other materiel of war at a rate required by its armed forces from the day hostilities begin until the day the war ends. Support at less than required rates could delay victory or cause defeat.
There are three methods by which a nation can provide sustained wartime support for its combatant forces. The first is to stockpile huge quantities of materiel and hope that victory would be won before the stocks were depleted. The second method is to deliver supplies in peacetime at required wartime rates; however, this solution could bankrupt a nation, because military unique items, such as ammunition, have little or no usage in peacetime.
The third method is the D to P logistics planning concept by which wartime support requirements will be satisfied by a balanced mix of assets on hand on D-day and assets gained from wartime production through P-day, the specific day when the national production rate for a given item equals the rate of wartime consumption. War plans based on the D to P concept require extensive and detailed analysis of materiel requirements and production capability. It is not uncommon to have different P-days for the ammunition and for the weapon that fires the ammunition or for a major component and the principal item that it supports. This concept is the basis for logistics management analyses and represents the qualitative computerized model for determining the upper limit of peacetime stockpiles and mobilization planning in support of wars whose duration cannot be predicted.
This concept is equally applicable to wars of short duration, such as strategic thermonuclear warfare, or to continental air defense. However, in these instances, primary reliance must be placed on stockpiling of supplies prior to D-day, for it is generally accepted that this type of warfare will be extremely intense and short in duration thereby placing little dependence upon post D-day production. It should be noted that planning for wars or short duration is based essentially on the number of targets that must be destroyed; therefore, wartime requirements determination is a relatively simple process inasmuch as there is a firm basis for planning. Such mission- or target-oriented planning is used extensively by the strategic retaliatory and continental air defense forces. However, in a nation, such as the United States, that is committed to reaction rather than preemption, it is exceedingly difficult to determine support requirements on a mission- or target-oriented basis for its general purpose forces. Whereas in the Arab-Israeli War of 1967 the Israelis could count the tanks, aircraft, and other materiel that had to be destroyed and allocate ammunition accordingly, the United States cannot determine its requirements in such a manner. Our country must be prepared to react to aggression in support of its worldwide treaty commitments. This means that the U.S. general purpose forces could be employed almost anywhere in the world against the armed forces of one or more nations under various sets of circumstances.
The Need For A Logistics Computerized Model
The need for a logistics computerized model to link more closely the supply requirements of the commander in the field to the capability of the continental United States (CONUS) industrial base to manufacture them manifested itself early in the Vietnam war insofar as ammunition was concerned. The Army developed the Ground Munitions Analysis Study (GMAS) for control of ground munitions, and the Director of Logistics of the Joint Chiefs of Staff, with representatives of the Secretary of Defense, the military departments, and the field commanders, developed the Worldwide Controlled Air Munitions Report for control of air munitions. These two systems, which represent a practical ADP application of the D to P concept for the hot base situation, have proved to be most effective in realtime planning for, and support of, the free world forces fighting in Southeast Asia.
With the scaling down of operations in Southeast Asia, the various nodes, links, and elements that make the D to P concept must now be analyzed in greater detail to determine what peacetime resources are required to support the peacetime strategic concept of our nation. Even though the D to P concept can be simply stated—supplies on hand must last until wartime production equals wartime consumption—potential disaster lurks for the logistics planner who fails to consider all the elements required to maintain equilibrium in wartime: the pipeline overseas; initial allowances/basic loads/shipfills; wartime consumption; wartime production; and the status of the production base. These elements are the parameters whose demands must be met to provide required logistics support, and there are so many of them that effective planning on a realtime basis must make extensive use of computerized models that simulate all of these elements.
Not only is there a need for a computerized model simulating the flow of supplies from procurement to consumption, but there is also a need for supporting computerized models. For example, although the military consumer is concerned primarily with the end item he orders, the CONUS-based logistician is concerned with the procurement leadtimes of the pacing components of the manufactured end items. Therefore, a manufacturing model synchronized with the D to P model for the end item will enable procurement and production specialists to determine rapidly the best courses of action to follow when requirements change.
In the sections that follow, all of the elements that make up the D to P concept are described. These are the elements that have been included in the computerized models used in the overall management of ammunition within the Department of Defense. Expansion of these techniques to improve realtime response offers a challenge to the logistician.
The Pipeline Overseas
Support of operations overseas means extended use of sealift, because it is estimated that even in the era of the C-5A cargo aircraft 80 percent of all cargo and supplies required to support sustained operations will travel by surface means due to the magnitude of the tonnage involved. Surface travel presents a network of interfaces that cause many complex problems for the logistician as he plans for the support of combat operations. A representative diagram of the nodes and links is shown in figure 1.
If figure 1 were divided into supply and cargo phases, a pipeline would be established. The shaded portion to the right presents that section of the pipeline relating to the delivery of supplies as items to the CONUS depots for consolidation and shipment as cargo (supplies which are packaged in bulk and are not generally available for issue as items) through the transportation network (center section) to the oversea depots where it is warehoused (shaded portion to the left) and ultimately delivered as individual items of supply to the military consumer. These sections represent the pipeline that links the military consumer with the civilian producer.
Some persons think of this pipeline as a network of pipes wherein one gets supplies whenever he opens the spigot—a system that is not unlike an urban water distribution system. Unless the level of the reservoir is maintained above the minimum outlet level, only the low-lying customers get the water—and they get it spasmodically as the pipes fill and discharge. Indeed, the military logistics system must optimize at the local depot or reservoir that supports the military consumer.
Other persons think of the pipeline in terms of individual items flowing through a network from source to destination. For most supplies, the pipeline is more analogous to wire communications: when one transmits, he pushes electrons at one end of a wire that is completely full of electrons thereby forcing out electrons at the receiving end. There are exceptions, however. They are the high-dollar, low-density (relatively low quantity per theater) items of supply that should be considered as individual items and shipped direct from CONUS base to ultimate consumer.
The important point to remember about the overall pipeline is the fact that the local supplier or depot must have supplies if assured support is to be given the ultimate consumer. Therefore, the local depot must be authorized sufficient quantities to insure that their stocks are always above minimum levels. The size of these levels depends on many factors, such as the characteristics of the items; their importance to the commander; rate or consumption (attrition); necessity for reserve stocks to cover unplanned operations or unscheduled losses; method of transportation into and out of the depot; frequency of shipments into and out of depots; rate at which cargo can be processed through arrival ports to the depot (throughput operations); and the rate at which cargo can be converted into items of supply (warehoused) by depot personnel.
In view of all the considerations affecting the size of pipeline levels, it is essential that analyses of required levels be conducted on an item-by-item basis. Such an analysis must consider all nodes and links of the shaded sections of figure 1.
Supplies must be available in the supply system to insure a continuous flow from producer to consumer. As long as the pipeline is full, supplies can be delivered at the computed rate from the day that hostilities begin. The depots are analogous to the reservoirs in a water distribution system: one located overseas near the consumer and the other situated near the producer—each having minimum and maximum levels to insure steady flows to the ultimate consumer in the first instance and into the intertheater transportation system in the second instance.
Initial Allowances/Basic Load/Shipfill
Even though there is a pipeline that links the ultimate military consumer with the civilian producer, the former also carries emergency supplies, and he carries them all the time—peace or war. The magnitude of this stockage depends on many factors, such as the ability of the military consuming unit to carry such stocks without degrading its operational capability, the distance at which the unit normally operates from supporting depots, and the rates of consumption and attrition. These supplies vary from the relatively small quantities carried by walking infantry to the large quantities carried by cruisers and aircraft carriers. The important characteristic of these supplies is the fact that the supply system always assumes that these levels are at 100 percent; any shortage is the basis for immediate replenishment. Hopefully, for high consumption items, such as ammunition, resupply will be on an automatic but controlled basis; desired levels must always be retained to permit the unit to function at maximum capability. As already noted in the section on the pipeline, operating and safety levels in the depots are designed to absorb the surges associated with fluctuating demand.
Wartime Consumption/Wartime Production
If peacetime production equalled wartime consumption rates, there would be no problem in converting from a peacetime to a wartime situation. However, this will rarely be the case; it can be anticipated that wartime consumption will not only exceed peacetime production but, at the outset of hostilities (D-Day), will increase at a rate faster than the production base can increase outputs. If the post D-day consumption and production curves were drawn, they would resemble those shown in figure 2.
As can be seen, the consumption curve rises more steeply than does the production curve with both curves becoming equal on P-day—the day, by definition, when the wartime production rate for a given item equals rate of wartime consumption. It is the net deficiency as shown in the shaded section that must be accommodated by peacetime provisioning to insure continuous supply at required rates.
Although figure 2 is more indicative of the nonlinear increases that could be anticipated once hostilities start, figure 3 better illustrates the need for providing peacetime stocks to cover the difference between wartime production and wartime consumption. This figure assumes that wartime consumption rises immediately to 30 items per period on D-day and stays at that level and that post D-day production rises linearly until P-day once the cold base is converted to a producing base. This figure also shows that the D to P stocks required on D-day are in addition to, and not a part of, the stocks required to support the pipeline overseas.
If figure 1 were expanded to show both the wartime consumption and production from D-day to P-day, the peacetime stockage to support the ultimate military consumer from D-day to P-day would be as shown in figure 3. It is emphasized that, with the exception of post D-day production (lightly shaded area in the figure) and consumption, all stocks should be physically available in the system on D-day to insure smooth support of the military consumer in the field. Any shortages in any of the levels will mean that the ultimate wartime consumer will be restricted in the rate at which he can consume supplies. These stocks are provided to cover specific functions in the pipeline from the factory to the ultimate consumers. To cut back on the pipeline level for reasons other than improvements in the rate of transporting or processing of supplies will only result in spasmodic and uncertain delivery rates at the receiving end. The elimination of depot stocks by shipping direct to the ultimate consumer places an inordinately expensive requirement on military resources due to the necessity to ship items in a "ready for use" condition. This practice often results in large backlogs of shipping or "delivered but lost supplies" as were experienced during the early days of the buildup in the Republic of Vietnam. Before any attempt should be made to cut back on stockage levels, a detailed analysis of each node and link are required, commencing with the most inhibiting. Ultimately there will be a need to optimize among transportation means, port throughput capabilities, depot stockage levels, intratheater shipments, and manpower because increasing the delivery rate or supplies depends directly upon improvements in the weakest of these links.
D to P Reserve Stock Computations
The key factor in all D to P computations is the anticipated wartime consumption rate, which must, by necessity, be based on analysis of such factors as experience gained in prior wars or "guesstimates" determined by engineering estimates for newly developed items—or by a combination of both.
Once a consumption factor has been determined, it is multiplied by the total number of days intransit time plus the summation of the days required to support the various operating and safety levels to determine the required overall pipeline stockage levels. To this level must be added the basic load or items carried by the ultimate military consumers and the D to P stocks required to compensate for the difference between the sum of wartime production and wartime consumption (fig. 2) during the D to P period.
The D to P stocks depend not only on the rate at which items are consumed but also on the rates at which they are produced. Therefore, the inventory objective is not a fixed objective once consumption rates are known. It depends almost exclusively on the status of the production base.
Figure 4 represents the various types of production bases that could exist on any given D-day: hot (production line producing quantities equal to wartime consumption); warm (minimum economic production rates not related to wartime consumption requirements); standby or cold (situation in which adequate production facilities are not operated before D-day but are maintained in idle standby. Average standby maintenance costs are low—generally less than 1 percent or less of replacement costs); and new or converted (situation in which facilities must be constructed new or converted from civilian use after D-day—generally caused by disposal of obsolete or expensive to maintain facilities).
Figure 4 does not show any decrease in assets for the hot base condition, since by definition production on D-day is equal to wartime consumption. Therefore, P-day occurs simultaneously with D-day, and the quantity P1, as represented on the ordinate axis, is equal to the D-day pipeline assets required to support the deployed forces. This pipeline level is identical for each condition of the production base. If requirements have been computed properly, all P-day levels will be the same as shown in figure 4.
The establishment of a new or converted base (curve 4) on the other hand would require the maximum quantity of D to P reserve stocks due to the length of time that it will take to establish new facilities or convert from civilian production. Peacetime procured stocks (DP) gradually decrease as they provide support until the day on which production equals wartime consumption (P4). If the dynamics of the situation have been properly considered (accurate requirements determination, full pipeline, full basic load, etc.), there will be no net buildup in assets after P-day, for items would be consumed at the same rate as they are produced and equilibrium would be reached. If the war were to end suddenly on P-day and production deliveries were not cut back, assets would build up along one of the appropriate dashed lines as shown in figure 4.
Therefore, analyses are required to determine the minimum quantities of any given item that will be produced after hostilities cease due to the lag time between contract cancellation and delivery of prior order production. Once the irreducible minimum quantity is known, the next objective is to examine the production base to determine what type of base should be maintained (warm, standby or cold, new or converted) in peactime. As soon as this decision is reached, wartime production should be phased back on an economic basis until it either cools down completely or continues to function as an economic warm base in peactime.
Overall D to P Support
In summary, the total peactime stockage required to support wartime consumption from D-day to P-day is equal to the sum of the initial allowances/basic load/shipfill plus the oversea stockage objective (operating and safety level) plus the intransit pipeline level (airlift or sealift as appropriate) plus the CONUS stockage objective (operating and safety level) plus the difference between wartime production and wartime consumption during the period between D-day and P-day. If these stocks are provided, the dynamics of the D to P concept are met, and support can be provided on an indefinite basis once hostilities start wherever U.S. forces may deploy.
This D to P concept represents the logistics equation that must be solved by logistics and mobility specialists. It can be anticipated that the various parameters will change as the battle is joined and new experience is gained but regardless of the factors involved, the principles are sound—a combination of assets on hand on D-day and wartime production deliveries to the ultimate user must be made to equal wartime consumption or the war will end on terms unfavorable to the United States. As the actual consumption rates of war change, so must the consumption variable of the D to P logistics model change.
There is a need to evaluate, on a continuing basis, all the links and nodes of the elements that make up the D to P concept and, once hostilities start, to make adjustments in the light of wartime operations. Such realtime computations are a big order, and only by extensive use of computerized models that simulate all of the parameters—variable as well as fixed—can logistics and mobility specialists forecast requirements and direct procurement on a timely basis.
Colonel Winfield S. Scott, USA, is the project manager for the 2.75-inch rocket system, Picatinny Arsenal, Dover, New Jersey. Before assuming this position in July 1968, Colonel Scott was assigned to the Plans Division, Logistics Directorate, Joint Chiefs of Staff in the Pentagon. His last oversea assignment was as Ordnance Officer for General William C. Westmoreland and Senior Ordnance Adviser to the Chief of Ordnance of rite Republic of Vietnam Armed Forces. Colonel Scott is a 1944 graduate of rite United States Military Academy.
| Date Taken: | 12.13.2024 |
| Date Posted: | 12.13.2024 11:07 |
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