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Posted on Oct 30, 2006 in Front Page Features, Stuff We Like

The Practical Art of Moving Armies – On the Computer Screen

By Larry Levandowski

Capacity is also determined by the carrying capacity of the transport units assigned to the route. In games that model capacity, you will need to first calculate your supply need per turn, then ensure that your supply route has the transportation assets to support this.

In Civ IV, as an example, capacity is a factor only for ocean and air movement. Roads are not constrained, and you can run a hundred tank units over a route, never even cracking the pavement. Over water, on the other hand, each sea transport can only carry a limited number of units, thus available transport capacity is a constraining factor. For discussion, let’s say you are on the offensive and are moving land forces over a small sea. Based on expected enemy strength, you feel you will need to have four new units arriving in the battle each turn. Assuming you have enough cities to produce four units per turn, you will also need to insure you have sea transport capacity to support their arrival on the front. If it takes three turns for a galley to cross the sea, and each galley can hold three units, you will need twelve galleys to support this offensive. Why so many? Well, you need two galleys to move four units. If it takes three turns to cross, you not only need enough galleys to move one way, but you must also consider the three turns of the return trip. So, two galleys times six turns, equals twelve galleys.


A good logistician will also ensure that there are no capacity bottlenecks. Do this by examining capacity along the entire logistics line, from source, to end point. Bottlenecks will occur wherever your capacity is lowest along the line. If you have 100 miles of highway, with two miles of muddy road in middle. The lowest capacity along the “pipe,” and thus the bottleneck of your route, will be that stretch of muddy road. Upgrading infrastructure, or increasing transport units assigned at these low capacity points, is the key to the smooth flow of supplies.

These potential bottleneck locations also need to be protected. Any smart enemy commander will know that supplies and transports tend to back-up at these points; and transports are usually an easy kill. It is also possible for the enemy to create bottlenecks. Destroying roads, rail line, and mining harbors (as submarines can in War in the Pacific) creates a bottleneck in the movement of supplies, and is an easy way for the enemy to swing the balance in their favor.


Supply is the idea that you must have enough of the consumables of battle, where and when you need them. I can only think of a few games that actually account for supplies as a unique element; Matrix Games’, War in the Pacific, and Gary Grigsby’s World at War come to mind. For a game like Civ IV (and many RTS’s) however, the military units themselves are consumed in combat and therefore the this concept of “supply” applies to them.

Commanders, before and during major operations, must continuously judge how many units of supply are needed each turn. How is this calculated?

First understand what effort is expected. Do this by scouting, or estimating enemy strength. If you don’t know, guess high; experience always helps here. Then based on what you think you will face, calculate how many units or supplies, you think you will expend each turn. In Civ IV for example, if you expect to attack four cities, each with six units, you can probably expect to lose at least eight units in the attack of each city. The enemy will also be able to replace one more of their lost units per turn, so you will need nine new units per turn.

Nine units per turn? Well you can only produce two units per turn, so what to do? The answer is to create a stockpile. And this in itself may take some time. If you are planning on assaulting for four turns, you can expect to consume nine units, times four turns, or 32 units. Don’t forget that your cities will still be producing during your four turns of attack, so you do not need to stockpile those eight units (two units produced per turn, times four turns). Therefore, your stockpile will need 24 units (32 minus the eight produced). If you can only produce two units per turn, it will take you twelve turns to organize your stockpile; better get moving on it!

A stockpile needs to be located as close as possible to the action, but not so close as to be in danger of capture or enemy interdiction. Usually stockpiles are stacked in a secure location (a fortified hill in Civ IV, works well), close to the combat area Routes in and out of the stockpile must be the best possible. For games like War in the Pacific, where port capacity is modeled, stockpiles must be high capacity ports so as not to create a bottleneck. For typical RTS, where gathered resources are turned into combat units, having stockpiles close to the gathering activity is a key element to victory..

Rate of production of supplies is also a critical consideration.. As we have pointed out, in many RTS, “supplies” are actually the units consumed in battle. Unless you have overwhelming force, any campaign will have an element of attrition. The side that can produce the most combat power in the shortest time, will have an advantage. So building a war machine with a higher capacity output than the enemy, will win almost every time. Some general points to do this are:

1) Have as many “factories” as possible. When there is no penalty for idle factories (upkeep, cost of workers etc.), then build as many as you can. If there is a penalty for factories, then you will need to balance the number of factories against the drain on resources.

2) As already mentioned, shorten travel time for resource gatherers. When not possible, increase transport capacity. In a typical RTS, put a resource gathering building close to where the resources are. That way, workers don’t waste as much time in transit. Sometimes, this is not an option, so capacity must be increased (ie. by adding more workers) As the Japanese, in War in the Pacific, you can’t shorten the distance between Palembang and Osaka, but you can insure that more tankers are assigned to that critical oil route.

3) In games where components are assembled in order to complete units; bows and leather jerkns, needed for bowmen, or Kawasaki engines for Zero fighters, you must insure that your up-stream component production doesn’t slow your downstream final product output. In War in the Pacific for example, if Japan has a capacity to produce 110 Zeros, but only 55 Nakajima engines, then they will only produce 55 Zeros, no matter how big the Zero factory is. So before expanding that Zero factory, you will need to build more engine capacity.

Another important concept related to supply is to deny the enemy their supply chain. This is done by destroying production facilities, transports and denying him the use of resources. In an early game of Civ IV for example, taking an enemy’s horse, iron, and copper resource squares, can deny him the production of critical units and put you at an advantage.

In War in the Pacific, the Japanese roll through Indonesia in early 1942.
The Java Sea’s constricted sea lanes and numerous Dutch
airfields present a logistical challenge

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