Risk Assessment, 2nd Edition

10 Layers of Control Analysis

Georgi Popov¹ and Bruce Lyon²

¹ University of Central Missouri

² Brown & Brown

10.1 Introduction

The concept of using layers of protection or defense has been practiced throughout history as a matter of survival. As early as the fourth century B.C., the Roman army transformed its structure from a rigid phalanx (a body of troops in close array) to a much more flexible triple line, known as acies triplex. The triple line allowed for this layered approach to present the strong and numerous Roman infantries with multiple advantages. At that time, the Roman infantry formed a layered battle line consisting of three ranks:

• first and closest enemy lines – hastati (usually younger and less experienced legionaries),
• second line – principes (usually more experienced soldiers), and
• third and last line – triarii, who were often veterans also strong reserve.

A unique feature of the Roman infantry was the depth of its spacing. The deep three‐layer Roman arrangement allowed the continual funneling or metering of combat power forward as well as in defense in depth. Very often, there was even a fourth layer which was used in front of the first heavy‐armed array. This fourth layer were the velites or light‐armed infantry (javelinists, archers). They were set up in a loose, linear formation (Warry 2015). Figure 10.1 illustrates this layered approach.

Figure 10.1 ...