1. The Lanchester Equations of Warfare Explained Larry L. Southard
Dynamical Systems MAT 5932
The Lanchester Equations of Warfare Explained
Larry L. Southard
Saturday, April 15, 2017

2. Agenda History of the Lanchester Equation Models
Lanchester Attrition Model
Deficiencies of the equations

3. History
The British engineer F.W. Lanchester (1914) developed this theory based on World War I aircraft engagements to explain why concentration of forces was useful in modern warfare.
Lanchester equations are taught and used at every major military college in the world.

4. Two Types of Models Homogeneous
Both models work on the basis of attrition
Homogeneous
a single scalar represents a unit’s combat power
Both sides are considered to have the same weapon effectiveness
Heterogeneous
attrition is assessed by weapon type and target type and other variability factors

5. Useful for the review of ancient battles
The Homogeneous Model
An “academic” model
Useful for the review of ancient battles
Not proper model for modern warfare

6. Heterogeneous Models
CONCEPT: describe each type of system's strength as a function (usually sum of attritions) of all types of systems which kill it
ASSUME: additivity, i.e., no synergism; can be relaxed with complex enhancements; and proportionality, i.e., loss rate of Xi is proportional to number of Yj which engage it.
No closed solutions, but can be solved numerically

7. The Heterogeneous model
More appropriate for “modern” battlefield.
The following battlefield functions are sometimes combined and sometimes modeled by separate algorithms:
direct fire
indirect fire
air-to-ground fire
ground-to-air fire
air-to-air fire
minefield attrition

8. The Heterogeneous model
The following processes are directly or indirectly measured in the heterogeneous model:
Opposing force strengths
FEBA (forward edge of the battle area) movement
Decision-making (including breakpoints)
Additional Areas of consideration to be applied:
Training
Morale
Terrain (topographically quantifiable)
Weapon Strength
Armor capabilities

9. Decision Processing in Combat Modeling
Target Acquisition
Engagement Decision
Target Selection
Damage Perception by Firer
Physical Attrition Process
Accuracy Assessment
Damage Assessment
Attrition
Sensing
Command and Control
Movement

10. Lanchester Attrition Model
CONCEPT: describe the rate at which a force loses systems as a function of the size of the force and the size of the enemy force. This results in a system of differential equations in force sizes x and y.
The solution to these equations as functions of x(t) and y(t) provide insights about battle outcome.
This model underlies many low-resolution and medium-resolution combat models. Similar forms also apply to models of biological populations in ecology.

11. The Lanchester Equation
Mathematically it looks simple:

12. Lanchester Attrition Model - Square Law
Integrating the equations which describe modern warfare
we get the following state equation, called Lanchester's "Square Law":

13. These equations have also been postulated to describe "aimed fire".
measures battle intensity
measures relative effectiveness

14. Questions Addressed by Square Law State Equation
Who will win?
What force ratio is required to gain victory?
How many survivors will the winner have?
Basic assumption is that other side is annihilated (not usually true in real world battles)
How long will the battle last?
How do force levels change over time?
How do changes in parameters x0, y0, a, and b affect the outcome of battle?
Is concentration of forces a good tactic?

15. Lanchester Square Law - Force Levels Over Time
After extensive derivation, the following expression for the X force level is derived as a function of time (the Y force level is equivalent):

16. Square Law - Force Levels Over Time
Example:
x(t) becomes zero at about t = 14 hours.
Surviving Y force is about y(14) = 50.

17. Square Law - Force Levels Over Time
How do kill rates affect outcome?
Now y(t) becomes zero at about t =24 hrs.
Surviving X force is about x(24) = 20.

18. Square Law - Force Levels Over Time
Can Y overcome this disadvantage by adding forces?
Not by adding 30 (the initial size of X's whole force).

19. Square Law - Force Levels Over Time
What will it do to add a little more to Y?
This is enough to turn the tide decidedly in Y's favor.

20. Square Law - Who Wins a Fight-to-the-Finish?
To determine who will win, each side must have victory conditions, i.e., we must have a "battle termination model". Assume both sides fight to annihilation.
One of three outcomes at time tf, the end time of the battle:
X wins, i.e., x(tf) > 0 and y(tf) = 0
Y wins, i.e., y(tf) > 0 and x(tf) = 0
Draw, i.e., x(tf) = 0 and y(tf) = 0
It can be shown that a Square-Law battle will be won by X if and only if:

21. Lanchester Square Law - Other Answers
How many survivors are there when X wins a fight-to-the-finish?
When X wins, how long does it take?

22. Square Law - Breakpoint Battle Termination
How long does it take if X wins?
(Assume battle termination at x(t) = xBP or y(t) = yBP)
In what case does X win? If and only if: