CASE STUDY CONCEPT: Military Logistics 101 — “An Army Marches on Its Stomach.”
In the spirit of the saying, “amateurs talk strategy and professionals talk logistics”, lets look at the campaigns of Alexander the Great. For those who think that his greatness was only due to his ability to dream up bold moves and cut a dashing figure in the saddle – think again.
Alexander was a master of supply chain management and he could not have succeeded otherwise. The authors from Greek and Roman times who recorded his deeds had little to say about something so apparently unglamorous as how he secured supplies for his army. Yet, from these same sources, many little details can be pieced together that show the overall supply chain picture and how Alexander managed it.
Modeling Alexander’s Supply Chain
A modern historian, Donald Engels, has investigated this topic in his book Alexander the Great and the Logistics of the Macedonian Army (Engles, Donald W., 1980, Alexander the Great and the Logistics of the Macedonian Army, Los Angeles, CA: University of California Press). Using information from Donald Engel’s book we have created a model of Alexander’s supply chain that supported his campaign in Afghanistan.
As this case begins, it is the year 329 BC. In the previous year Alexander defeated the Persian King Darius, and now he’s organizing a supply chain to draw on the farms and workshops of Persia to support his advance into Afghanistan and beyond. The screenshot below shows the supply chain he has created so far. This case study will give you insight into what Napoleon meant when he said, “An army marches on its stomach.” An army can only go where there are supplies to support it (or it will perish).
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The orange arrows show Alexander’s planned route of march, and his first objective, Kabul, is circled in yellow. On the left side of the screen above as the supply chain crosses from Persia into Afghanistan is the city of Herat. This city was the logistical base from which Alexander launched his campaign into Afghanistan and Central Asia.
Alexander Used Logistics as a Competitive Advantage
Alexander’s army had a logistics structure that was fundamentally different from other armies of the time. In other armies the number of support people and camp followers was often as large as the number of actual fighting soldiers. This was because armies traveled with huge numbers of carts and pack animals to carry their equipment and provisions. And those carts and pack animals needed lots of people to tend them. In the Macedonian army the use of carts was severely restricted. Soldiers were trained to carry their own equipment and provisions. Other contemporary armies did not require their soldiers to carry such heavy burdens but they paid for this because the resulting baggage trains reduced their speed and mobility.
The result of the Macedonian army’s logistics structure was that it became the fastest, lightest, and most mobile army of its time. It was capable of making lightning strikes against an opponent often before they were even aware of what was happening. Because the army was able to move quickly and suddenly, Alexander could use this capability to devise strategies and employ tactics that allowed him to surprise and overwhelm enemies that were numerically much larger.
The picture that emerges of how Alexander managed his supply chain is an interesting one. For instance, time and again the historical sources mention that before he entered a new territory, he would receive the surrender of its ruler and arrange in advance with local officials for the supplies his army would need. The city of Herat in Afghanistan was founded by Alexander at the start of this campaign to be the main supply depot for his army of some 64,000 troops and about 10,000 cavalry horses. Added to this were camp followers equaling maybe another 35,000 people plus pack animals such as camels and horses or mules for pulling wagons and carts.
Herat was a logical place to locate the main supply depot as shown in the screenshot below. It was a central place to collect supplies from the surrounding regions, and it was itself a large food producing area. Supplies coming from Persia followed roads going east along the river. Supplies were also delivered by roads coming from agricultural areas to the north, and by roads coming west along the river. The flat plain at the foot of the mountains where the roads came together was next to a river crossing, and this made it a good place to build warehouses to store the supplies that were delivered.
Next to the warehouses were buildings to house the people who worked there and the troops that protected them. There were shops and restaurants to serve these people, and on a rocky ridge overlooking the city Alexander built an impressive citadel shown below to guard the city. He named this city Alexandria Ariana. From here supplies could be loaded onto wagons and pack animals and sent south on the route through the desert toward Kabul that was used by Alexander’s soldiers.
(Citadel of Herat – By Norbert Nelte Flipper – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=67529460)
If a region did not surrender to him in advance, Alexander would not commit his entire army to a campaign in that land. He would not risk putting his army in a situation where it could be crippled or destroyed by a lack of provisions. Instead, he would gather intelligence about the routes, the resources, and the climate of the region and then set off with a small, light force to surprise his opponent. The main army would remain behind at a well-stocked base such as his supply depot at Herat until Alexander secured adequate supplies for it to follow.
Estimates and Assumptions for Alexander’s Supply Chain
We will make a few simplifying assumptions about Alexander’s supply chain as described by Professor Engel. We’ll use the following estimates to define basic logistics operating parameters for this case study (you can easily change these numbers in the supply chain model if you want to use other estimates):
- For products we’ll use a generic unit of inventory which is a mix of required products in a 1 cubic meter package. We’ll call this inventory “All Purpose Material” (APM)
- 1 unit of APM has a cube volume of 1 cubic meter and cube weight of 40 kilograms
- 1 unit of APM can sustain 5 soldiers for a day; each soldier requires 0.2 units of APM per day; that’s 8 kilos of supplies per soldier per day
- So it takes 2,000 units of APM per day to support 10,000 troops; 500 units of APM will support 2,500 troops per day
- Assume Alexander needs to support 20,000 soldiers on this campaign. Some of these soldiers will be at the head of the advance to do the fighting and some will be spread out along the length of the advance to operate and protect the supply line.
- Alexander’s supply chain vehicles are wagons drawn by horses or mules; a wagon has a carry volume of 5 cubic meters and a carry weight of 200 kilograms
- A wagon has a speed of 3 kilometers per hour
- A wagon can carry 5 units of APM and support 25 troops per day
- 100 wagons can support 2,500 troops per day
- Vehicles can be units of 50 or 100 or 200 wagons
- The route shown for Alexander’s march on Kabul is the only practical route to move and supply 20,000 troops using technology available to Alexander
There was no fortress in Kabul at the time when Alexander passed through, but we introduce the fortress and its capture as a way to explore a (relatively) simple initial logistics problem. That problem is the support of a large body of troops concentrating in a single location before a battle. As the case progresses, we will move on to tackle more challenging logistics problems associated with supporting columns of troops on the march.
Alexander once said, “My logisticians are a humorless lot… for they know if my campaign fails, they are the first ones I will slay.” Imagine you are in charge of Alexander’s supply chain. He has sketched out what he wants to do and now he’s looking to you to create and operate the supply chain that will support his Afghan campaign. His first objective is to capture Kabul. How will you deliver the supplies his troops need to achieve that objective?
FIRST CHALLENGE —Alexander’s plan is to march to and capture the Afghan fortress at Kabul, and then move on further into Afghanistan from there. Can you create a supply chain to support this campaign? That’s a pretty theoretical question until you start playing with the design of different supply chains and learning from simulations about what works and what doesn’t.
Objective: Design a supply chain that supports 8,000 troops who operate and defend the supply chain, and 12,000 troops concentrated at a staging area outside of Kabul. Get the supply chain to run for 15 days.
At the start of this campaign there are factories set up in three locations in Persia to produce food, weapons and other needed material. Inside Afghanistan there are supply depots established in Herat and Shindand. And there are military bases at Delram and Kandahar. For this challenge we focus on an advance force of 20,000 troops out of Alexander’s total army of about 64,000. The screenshot below shows Alexander’s supply chain as he advanced into Afghanistan toward Kabul. It shows operating results from the first simulation run of the model of Alexander’s supply chain from the online library.
We can see the depot at Herat runs out of storage space for supplies (red circle indicates point of failure), and at the same time supplies on hand at Kandahar (circled in blue) are being consumed faster than they are delivered. Two upward spikes in the otherwise downward sloping blue line on the graph show arrivals of wagons carrying supplies. But arriving supplies do not keep up with daily demand. More wagons are needed to move up more supplies. And it would be helpful to find new sources of supply closer to Alexander’s area of operations (AOR).
Notice in the screenshot above there are two facilities marked with blue arrows just to the south of the supply chain delivery route. Both of these facilities are located in or near fertile desert farming areas made possible by irrigation works built by the local inhabitants.
Switch to the satellite view (button in upper left corner of screen) and zoom in on these facilities. See the green, agricultural land following along the course of the rivers as they flow through the desert landscape. These two facilities are large producers of APM and they can deliver supplies to the army. The screenshot below shows a satellite view of the agricultural land around Gamsir and a route for delivering supplies from Gamsir to Kandahar.
As you extend the supply chain toward Kabul, you need to set up a new facility that will be the staging area just outside Kabul where your troops will concentrate for the attack on the fortress. And then deliver supplies to support the 12,000 troops there. You may want to set up another base or supply depot to protect the supply route between Kandahar and Kabul. Each new facility requires storage space and soldiers to protect it. As you create this supply chain and run simulations you will get an intuitive feel for what it is like to run a supply chain under the conditions in which Alexander and his soldiers operated (and although the wagons are faster, things are not that different for armies today).
Some things to think about as you work with this first challenge:
- Existing facilities can be expanded to become depots by increasing their storage capacity so supplies can be stockpiled in them to support deliveries of supplies to facilities further along the supply chain
- Establish a forward base to hold the 12,000 troops who will attack Kabul. This base should be about a day’s march outside of Kabul (40 – 45 km); just inside of the yellow circle around Kabul shown in the screenshots above — pick a location for this base and explain why that is a good location.
- How will you move up enough supplies to support those troops in the forward base for 15 days?
- Define the number of vehicles at each facility and their routes and product delivery quantities.
- You may want to establish another facility for storing supplies in between Kandahar and Kabul — explain why you did or why you did not.
- Remember to adjust demand for APM at each facility to supply the troops stationed at those facilities to protect them
- Assume the closer you get to Kabul the more troops need to be stationed at a facility to protect it and to escort the supply convoys
- Experiment with the number of wagons needed to support different allocations of troops in different facilities. How many wagons do you need?
- Are you starting to understand how difficult it is to supply large numbers of troops as they advance across enemy territory?
- What will Alexander say when you tell him how many wagons you need?
SAVE BACKUP COPIES of your supply chain model from time to time as you make changes. Click “Save” button next to your model in Account Management screen. There is no “undo”, but if a change doesn’t work out, you can restore from a saved copy. And sometimes supply chain model files (json files) become damaged and they no longer work, so you want backup copies of your supply chain to restore from when that happens.
SECOND CHALLENGE — Alexander thinks you are asking for way too many wagons. Find ways to streamline and redesign your supply chain to do more with less.
Objective: Reduce use of wagons as much as possible while still delivering supplies needed to support 12,000 troops at the staging area outside Kabul for 15 days.
Hint: Alexander and other armies of that time lived off the land; they requisitioned local supplies from towns they passed through. From your work on the first challenge you can see why. It takes a huge number of wagons to transport all the supplies needed by an army. So it is best to requisition supplies of food, wood, cloth, leather and other commodities from local sources. Use wagons only to carry the hard to find or make items such as heavy weapons, armor, tents and cooking utensils.
Alexander timed his campaign to begin early in the spring as the first harvests of winter wheat were made and the grain became available at storehouses in the cities he passed through. Assume most of the APM needed by the army (about 85 percent) is food, water and other material (cloth, leather, wood, metal) that could be acquired locally. Alexander’s army carried some of their supplies, such as armor, weapons and tents, and they requisitioned or purchased the rest of what they needed from villages and cities along the way. The screenshot below shows a satellite view of Gamsir and the productive farming made possible by irrigation works that diverted water from the river to the grow grain and vegetables in the fields along the river valley.
In all these screenshots notice the green strips of cultivated land that follow the rivers through this otherwise desert landscape; that is where much of the food and other supplies were (and still are) produced. Assume you can meet 85 percent of demand for APM from locally produced sources. This significantly reduces the demand for wagons to move APM over long distances. And if the soldiers carried some of the APM themselves it further reduces the demand for wagons. Assume each soldier can carry weight up to 30 kg and volume up to 0.2 cubic meters.
Acquiring Supplies Locally Reduces the Need for Wagons
In the supply chain model the facilities each have daily production rates for APM to represent the amount of food and raw materials they produce. Assume the Zarangea facility has 200 wagons available for delivering APM to another facility such as Delram. Assume there are 150 wagons available at Garmsir and they can be used to supply APM to Kandahar. Also assume Kandahar produces 900 units of APM per day itself because as shown below, you can see it is situated in the middle of a green agricultural region like Garmsir.
If you put new facilities in locations between Kandahar and Kabul that are also located in agricultural areas that support production of food and raw materials, then you will need fewer wagons to haul the remaining supplies needed by the army. Switch to satellite view and zoom on the route the army will take to Kabul. Look for areas that show concentrations of agricultural activity. Those make good locations for new depots and forward bases needed to support Alexander’s advance on Kabul.
Assign daily production rates for APM to these facilities based on how much green land you see around these facilities; the more green land the higher the production rate. Use Garmsir and Kandahar as points of reference for your estimates – see how much bigger or smaller are these areas of green land compared to Garmsir or Kandahar.
Things to think about for this second challenge:
- If 85 percent of needed APM can be acquired locally, how many wagons are required to make this supply chain work?
- How much APM needs to be produced at facilities between Kandahar and Kabul and how much needs to be delivered from other facilities to support the troops?
- Where would you put the new facilities and why? How many troops would you station at each facility to protect it and why?
- For ideas on how to expand this supply chain see “Tips for Building Supply Chain Models” for useful techniques. There are also useful ideas to be found in the section “Reducing Inventory and Operating Costs”
THIRD CHALLENGE – Alexander’s strategy calls for the army to continue its advance after taking Kabul. The army will live off the land on this march. Troops and wagons will carry the equipment they need (armor, tents, weapons, utensils) and they will buy or requisition the rest from cities and towns they pass through (85% of daily APM requirements). Alexander wants your plan for how to keep the army supplied on the march, and he wants your logistics plan to support his strategy of moving quickly and surprising his opponents.
Objective: From Kabul Alexander will take a fast, light force of 11,000 infantry and cavalry troops and move north toward the cities of Bukhara and Samarkand (circled in yellow). Create a supply chain design that merges battle strategy and logistics to give Alexander the military advantage he needs for success in this campaign. Define routes of advance that meet the army’s need to acquire supplies and also enable the army to move quickly and surprise its opponents.
Alexander’s forces will need to cross over the Hindu Kush mountains north of Kabul so find mountain passes they can use. Once over the mountains, there are many cities and agricultural areas where supplies can be acquired. Identify routes through those cities for the army as it makes its way to Bukhara and Samarkand.
Assume 6,000 troops are needed to capture Samarkand and 5,000 are needed to capture Bukhara. Find routes for 6,000 troops to reach Samarkand and for 5,000 troops to reach Bukhara. You can explore sending troops on just one or two routes to the two cities, or you may find multiple routes for different sized units. These routes must enable the units that follow them to converge in appropriate numbers on the two cities. All units need to arrive at their designated cities within a day or two of each other.
We are modeling a special sort of supply chain here. It is composed of a series of one-time, one-way transactions that occur as Alexander’s army travels across the landscape toward its objectives. The only thing that matters is creating a plan of advance where all units are able to pick up the supplies they need as they travel, enabling them to reach their assigned cities in a timely manner.
Modeling and Simulating the Plan of Advance
Their destination on the other side of the mountains was the vast plains of Central Asia, and the rich agricultural and trading cities that spread out across those plains. The troops made their way over the mountain passes as quickly as they could, and carried the food they needed with them because there is little food to be had in the high mountains. The scenery as shown below is awe inspiring, but the nights are cold and the air is thin.
(Mountains of the Chitral Valley by Emaad Paracha – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=59432953)
Once over the mountains, the army emerged onto the plains near the city of Kunduz as shown in the screenshot below. The long river in front of them was known as the Oxus (now the Amu Darya). Where do you think Alexander would choose to cross the river (and also get food for his soldiers when he crossed)? He crossed the river at the spot where the modern city of Termez now stands. A city stood there in Alexander’s time and it was a rich food producing area so Alexander knew he could get food for his troops as he passed through.
After crossing at Termez, going northwest along the river offers one possible route of advance on the city of Bukhara. However that is the route an opponent would most likely expect Alexander to take so it would probably be more strongly defended. What other routes can you find to advance on Bukhara? And what route would you pick for the advance on Samarkand? Would you pick a route that crosses another mountain range, or would you look for a route that goes around the mountains?
If you were opposing Alexander where would you concentrate your army? Would you plan to stop him as he tried to cross the river, or would you pick a different location? Why?
In the screenshot below (map view with Terrain feature turned off) you can see the road network that exists today. In many cases, maybe most, the existing roads follow in the tracks of ancient roads and trails. That is because the ancient roads followed river valleys and the flattest land, and took the shortest routes between cities whenever possible. That is why modern roads also use those routes; they are still the best way to travel across this landscape.
So we will use the modern road network as a good estimate of the routes that were available to Alexander. You can also create new roads if you want, just make sure they are roads that Alexanders army could handle. Long stretches of water-less desert and steep mountains are not routes that an army on foot or horseback could handle (they’re hard on modern armies too).
Because the army is living off the land and not staying in any location as it moves toward the two cities, a good way to model this supply chain is to think of different sized units in Alexander’s army (500 men, 1000 men, 2000 men etc.) as being vehicles. These vehicles can use different routes to get to their final destinations of Bukhara and Samarkand. The starting location for all vehicles is Kabul. Find routes that support different sized vehicles as they move from facility to facility on multi-stop routes that advance them toward their assigned cities.
Assume units of Alexander’s army can carry up to four days of supplies with them. Represent smaller units (up to 1000 soldiers) as a medium size truck with a speed of 6 km/hr., and for larger units use a large truck with a speed of 3 km/hr. Plot routes for these vehicles to follow. Given the speeds at which units can move and the distances involved, it will take some number of days for the units to travel from one facility to the next.
You can see travel times and distances in the Edit screen when you create a route between two cities. Use those travel times to calculate pick-up quantities at each stop on a unit’s route of advance. If it only takes half a day to reach a given facility, then the vehicle picks up half its daily needs. If it takes 3 days, it picks up three times its daily needs. And remember, a unit does not have to pick up supplies at every facility it passes through, but no unit can go for more than four days without resupply from a facility it does pass through.
Routes of March are Guided by Considerations of Logistics
As a general rule, you want to pick routes that follow rivers and go from one green agricultural area to the next as units move toward their assigned cities. The facilities on the routes you choose must be productive enough to generate adequate on-hand inventory to fill the pick up amounts of the units (vehicles) that pass through. Assign each facility a daily production rate and an initial on-hand amount of APM related to the size of the farmland surrounding the facility.
Estimate initial on-hand amounts of APM based on the amount of green farmland surrounding these facilities. Make educated guesses about the size of the spring harvest for each facility and deduct some APM to account for local demand, the remainder is the initial on-hand amount. Use the facilities of Gamsir and Zarangea as the basis for your estimates. How much more or less green agricultural land do you see around other cities as compared to Gamsir and Zarangea?
You will need to zoom in and look at these cities and their surrounding agricultural areas carefully. The more surrounding farmland, the higher is the initial on-hand amount of APM, and the higher the daily production rate. Make your best estimates and be prepared to explain why you made those estimates.
Create a plan where the simulation shows all units can reach the city they are assigned to attack in a timely manner. And where the simulation shows all units can make this trip while picking up the supplies they need at stops on their routes. Show the planned route of advance for each unit as a multi-stop delivery route. A vehicle representing a unit will have the city it is assigned to attack as the last stop on its multi-stop route.
Consider dividing the army into smaller groups. This way each group has a smaller logistics footprint so there are more choices in selecting possible routes of advance. This gives Alexander more options for strategy in the campaign. It plays to a major strength of his army which was the ability to surprise and overwhelm larger opponents by moving quickly over the landscape because of its lighter and more agile supply chain (fewer wagons, less equipment, soldiers trained to carry more).
Notes for Building this Model
In the simulations when units do reach their assigned cities they will then return to their starting location in Kabul, but that return trip can be ignored. Make the delay between departures for each unit a large number (1,000 hours). That way the vehicle representing each unit will return to Kabul where it will wait and not begin its route again during the simulation.
See Tips for Building Supply Chain Models and scroll down to the Routes section to see tips for creating vehicle routes between facilities if there are no existing roads on the map. But if you create a new route where no road currently exists make sure it is a route that an army on foot or on horseback could handle. Zoom in and turn on the Terrain feature and the satellite view to study the land over which your route will travel.
Set vehicle carry weights and volumes to a very large number to accommodate the amounts of APM they will pick up. In this model APM production rates at facilities and vehicle speeds and pick-up quantities are the determining factors, not vehicle carry weights and volumes (the APM picked up would be consumed day by day anyway). Also set storage capacity at Kabul to a very large number to handle the amount of APM on the returning unit vehicles.
Questions to think about as you work on this third challenge:
- Assuming the amount of APM on-hand at Kabul was captured intact, how long could Alexander’s troops occupy Kabul before needing to be resupplied? Given the rate of APM production by Kabul itself, how many troops can it support without additional supplies from elsewhere?
- If the whole army stayed in Kabul for four days, and then moved on leaving 1,000 troops behind to guard the fortress, how many days would the remaining supplies of APM support the troops who stayed in Kabul?
- Remember – you still need to keep the supply chain working to support the troops in Kabul and the other facilities along the supply chain stretching back to Herat
- How much of the APM supplies in Kabul could the departing troops take with them to consume on their march? How many days travel can they get with these supplies?
- What are the best places in between Kabul and Bukhara and Samarkand where troops could find food and other supplies?
- Would it be best to keep the army together in one group and advance first on one city and then the next – or is it best to divide the army into smaller groups that each advance independently on their assigned city? Why?
- If you decide to divide the army into smaller units, explain how you reconcile that decision with the warning, “don’t divide your forces in the face of a superior foe.”
- What routes of advance will you recommend to Alexander? What advantages do these routes offer – logistical and strategic?
As you work with this model and identify the possible routes Alexander’s army can take you will see how and why strategy and logistics are so tightly connected. You will appreciate how logistics affected strategy in Alexander’s time — and how it still does today.
MISSION REPORTING TEMPLATE — There is reporting template with an operations report and a performance dashboard for analyzing your simulation data. The template is built for a 15-day period. You can import your simulation data after trimming it for 15 days (scroll down to bottom of Analyzing Simulation Data). The operations report shows facility and product detail, and the dashboard shows where the best opportunities are for improvement. You can download a copy of the mission reporting template here.
The reporting template is set up for the Nepal Earthquake DR supply chain, but look at how the reports read the product and simulation data – you will see how to change the spreadsheet as needed to accommodate this case study.
This reporting template will be helpful for analyzing simulation results from the first two challenges. But it will not be very relevant for analyzing simulation results from the third challenge. In the third challenge the only thing that really matters is to find routes that enable all units (vehicles) to reach the last stop on their multi-stop routes — the cities they are assigned to attack. And to arrive at their assigned cities within a day or two of the other units also assigned to attack those cities.
To share your changes and improvements to this model (json file) with other SCM Globe users see “Download and Share Supply Chain Models”
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