fighting ability. The first three of these conclusions are obvious. The final one is the origin of the name "square law". Relation to the salvo combat model Lanchester's equations are related to the more recent salvo combat model equations, with two main differences. First, Lanchester's original equations form a continuous time model, whereas the basic salvo equations form a discrete time model. In a gun battle, bullets or shells are typically fired in large quantities. Each round has a relatively low chance of hitting its target, and does a relatively small amount of damage. Therefore, Lanchester's equations model gunfire as a stream of firepower that continuously weakens the enemy force over time. By comparison, cruise missiles typically are fired in relatively small quantities. Each one has a high probability of hitting its target, and carries a relatively powerful warhead. Therefore, it makes more sense to model them as a discrete pulse (or salvo) of firepower in a discrete time model. Second, Lanchester's equations include only offensive firepower, whereas the salvo equations also include defensive firepower. Given their small size and large number, it is not practical to intercept bullets and shells in a gun battle. By comparison, cruise missiles can be intercepted (shot down) by surface-to-air missiles and anti-aircraft guns. So it is important to include such active defenses in a missile combat model. Lanchester's law in use Lanchester's laws have been used to model historical battles for research purposes. Examples include Pickett's Charge of Confederate infantry against Union infantry during the 1863 Battle of Gettysburg, and the 1940 Battle of Britain between the British and German air forces. In modern warfare, to take into account that to some extent both linear and the square apply often, an exponent of 1.5 is used. Attempts have been made to apply Lanchester's laws to conflicts between animal groups. Examples include tests with chimpanzees and fire ants. The chimpanzee application was relatively successful; the fire ant application did not confirm that the square law applied. Helmbold Parameters The Helmbold Parameters provide quick, concise, exact numerical indices, soundly based on historical data, for comparing battles with respect to their bitterness and the degree to which side had the advantage. While their definition is modeled after a solution of the Lanchester Square Law's differential equations, their numerical values are based entirely on the initial and final strengths of the opponents and in no way depend