The deployment doctrine of the 18th Century army was different from that of earlier periods. Like their predecessors, western European armies during the early 1700s were normally deployed on the battlefield in a highly structured manner as one united entity, known as the "order of battle." The order, solidity, and security of a combined army were felt to be more important than the maneuverability of its individual parts. Unlike the Napoleonic era and beyond, linear armies were not yet organized into divisions or corps that could operate independently.

The largest permanently organized unit was the regiment, which could contain one to four battalions. These regiments fit into a specific position within an overall plan for the deployment of the army as one entity. The details of army deployment could vary from battle to battle, and there were always instances where large detachments were made to perform specific missions away from the main army, but the general principle was that the army was to form as a solid whole when a battle was imminent.

A typical army of the period marched onto the battlefield in a few long march columns. Using a "processional" (follow the leader) system of deployment that took hours to complete, the infantry unraveled from these long march columns into two multi-battalion lines of infantry spanning almost the entire length of the battlefield.

Every regiment had its position in the line predetermined by seniority. A second line of battalions deployed in rear of the first at a distance of about 300 yards to act as support. Each of the numerous battalions composing the first line abutted neighboring units to right and left to form a solid wall of troops. Only twelve yards separated the battalions deployed in the same line. Sometimes there were greater intervals between those battalions forming the second line.

Additional battalions were often deployed at right angles ("en potence" ) on the flanks, between the first and second lines, connecting them. The general idea of this deployment was to form the infantry of the army into one great rectangular box presenting no flanks that could be exploited by an attacker, especially cavalry.

It was considered ideal if one or both flanks of the infantry mass were protected by impassable terrain, such as a river. If a flank was not secured in this manner, cavalry was deployed on the exposed wing in order to provide support. Cavalry was usually posted on both wings, but in certain types of terrain might be deployed in rear of the infantry. If the army was large enough, a third line usually composed of both infantry and cavalry acted as a reserve.

Securing both ends, or flanks, of the infantry line was necessary because battalions deployed in thin firing lines were virtually helpless if attacked on flank by cavalry. This had not been true in earlier periods, when deep columns of pikemen presented no vulnerable flanks that could be exploited by cavalry - a "pike and shot" unit could defend itself on all sides, and could with relative safely stand unsupported on the battlefield - an island of resistance with the ability to repulse cavalry.

Another reason battalions needed to abut neighboring units during these early days of linear warfare was that it took battalions a long time to form from line into anti-cavalry defensive formations, such as closed column or square. The tactical evolutions that would allow battalions during the Napoleonic period to quickly change formation were not invented until the 1740s by the Prussians.

Using the analogy of a machine, every element of the early 18th century army was an integral part of the whole. Individual initiative by any commander was frowned upon. There was a place for everything, and everything was to be in its place (the general philosophy behind human activity during the Age of Reason). The universe was thought to work like a clock mechanism. To be regarded as a machine was the highest compliment during the 18th Century. Therefore, the only job of subordinate commanders at every level was to assure that the troops kept their formation and place in the battle line, supporting comrades to right and left.

Although this doctrine increased the security of the united army, it hampered the effectiveness of officers when they were entrusted with the execution of an independent maneuver, or presented with an opportunity when in action, because they were not accustomed nor encouraged to act on their own initiative.

This was the classic linear method of army deployment. It was very successful in securing the front of the army, while reducing the threat of flank attack upon infantry formed in thin lines. In fact, during this early period of linear warfare there are no definite examples of an infantry line in good order being destroyed by swift attack by cavalry on its flank, although there were instances where maneuvering cavalry eventually enveloped an infantry line, forcing it to retire or refuse a flank.

There were a few instances during Seven Years War (1756-63) of cavalry falling like a thunderbolt on the flank of infantry and destroying it in an instant - but only after the strictly regulated order of the infantry had been completely disrupted by tactical circumstances and casualties. It is not until the Napoleonic Wars that we find documented examples of what happened when a properly formed infantry line was caught in flank by cavalry.

For example, in 1811 at the battle of Albuera, during the Peninsular War in Spain, Colborne's British brigade was surprised on flank by the 2nd French Hussars and 1st Polish Lancers of the Vistula Legion as it advanced unsupported over open ground. Visibility was obscured by a heavy rain squall, which allowed the cavalry to close before the battalions could form square. Colborne's brigade was virtually annihilated in a few moments. Of the 1,648 officers and infantrymen in line when the cavalry attack began, 1,248 were rendered hors de combat in a few moments.

Another stunning debacle in Spain provides an even better example of what could happen to an entire army if the rules of linear army deployment were violated. In this case a Spanish infantry line was deployed in an open field, with no cavalry nor terrain feature protecting the left flank. The mistake cost the Spanish the battle of Medina de Rio Seco (1808). Sir Charles Oman describes the decisive moment in his history of the Peninsular War:

"Then came the development of BessiŠres' plan: Sabathier and Merle [infantry] were told to attack in earnest [frontally], and while Blake [the commander of the Spanish army] was deeply engaged with their fifteen battalions, LaSalle rode into the open space on the left of the Galicians, formed up the 22nd chasseursacheval at right angles to the Spanish line, and charged furiously upon Blake's flank. The unfortunate troops on whom the blow fell were deployed in line, and utterly unprepared for a cavalry shock from the side.

The first battalion which received the attack broke at once and ran in upon the second: in a few minutes Blake's whole left wing fell down like a pack of cards, each corps as it fled sweeping away that next to it....Blake's troops were only saved from complete destruction by the steadiness of a Navarrese battalion, which formed square to cover the retreat, and at the cost of one-third of its strength allowed the other corps to get a long start on their flight."

What seems to be an incredible accomplishment for a lone light cavalry regiment helps explain one sort of specter that haunted early 18th Century military men as they struggled to develop a cogent grand-tactical doctrine compatible with the battalion drawn up in a thin line.

Though an army drawn up in linear fashion was very strong on defense when in a chosen position, attempting to maneuver and attack with it presented many problems, because it was very difficult to move the long lines forward with any speed while maintaining the order and the continuity of the line of battle. For decades after the introduction of the flintlock musket made the linear battalion practical, leaders struggled rather unsuccessfully to overcome the many weaknesses of the linear system.

Yet regardless of all the impediments to maneuver it imposed upon armies, classical linear grand-tactical doctrine was extremely aggressive. The general principle was that the first line of the army, supported by the rest, was to assail the foe across his entire front with the intention of eventually deciding the issue with the bayonet.

However, as is often the case with positive change, new problems arise as the result of advantages gained, and classical linear doctrine brought with it severe disadvantages. An army drawn up securely in its carefully chosen position awaiting the attack of the foe cannot exploit victory, nor win a war, by standing only on the defensive. At some point the enemy must be attacked and beaten. Generals of the linear period understood this. In the French army the shock assault had often in the past been the means to gain victory, and the need for a fierce attack by the French soldier was a sort of military religion to them. Unfortunately, the weaknesses of the linear system became apparent once an army took the offensive. This is when reality tested theory, and theory was found wanting.

Once the armies made contact, the strict control necessary to maintain linear deployment usually broke down and chaos ensued. For example, imagine how difficult it was to march a thin line of attacking troops often a mile or more long across any type of terrain while maintaining formation and coordination, even when advancing straight ahead. In order to avoid crowding battalions to right or left, brigade commanders had to pick out a church steeple or some other "point of view" as a visual reference for the guide battalion to march toward and to use as a reference point.

The other battalions had to conform to the movements of the guide battalion, and the brigades to each other, and so forth. That was difficult enough, especially if smoke or the vagaries of terrain obscured the point of view. But if a line of advancing battalions was required by circumstances to wheel in order to change front, even slightly, or if some terrain difficulty was encountered by a part of the line, the possibility that the entire line would fall into confusion and/or break connection with adjoining units increased significantly. Add to this that the soldiers of most armies were not marching in cadenced step, which hampered the maintenance of order even within each battalion, and a recipe for chaos is born.

More From Breitenfeld to Waterloo The Origins of Napoleonic Infantry Tactics

Introduction
Infantry in the Early Musket Era
The Flintlock Musket Revolutionizes Warfare
The "Order of Battle" During the Classical Linear Period
Firepower vs. Shock
Further Reading