As upright mammals, all of our fighting implements – fists, feet, nails, and teeth – are to the fore. Our back and sides, unarmored and unprotected, remain exposed and vulnerable during combat. However, aligned side-by-side, friendly warriors, barring those on the line’s very ends, can protect each other’s flanks and rear. When one warrior fights, holds her position in line, those around her can focus their effort on striking out at the opponent. Without having to fight any harder, by simply fighting together, every warrior is more effective.
The line is a feature of warfare in all its forms and epochs. However, its length, shape, continuity, the distance between neighboring warriors, or the number echeloned are relatively un-important characteristics. These geometrical dimensions have varied across societies, through time, and even throughout the duration of a single engagement. The key characteristic of a line is its perceived permanence. Does a warrior believe the line will hold?