Oblique order

The oblique order is a military tactic whereby an attacking army focuses its forces to attack a single enemy flank. The force commander concentrates the majority of his strength on one flank and uses the remainder to fix the enemy line. This allows a commander with weaker or equal forces to achieve a local superiority in numbers. The commander can then try to defeat the enemy in detail. It was most famously used by the armies of Frederick II of Prussia. Oblique order required disciplined troops able to execute complex maneuvers in varied circumstances.

In the oblique order attack, the commander of the army would intentionally weaken one portion of the line to concentrate their troops elsewhere. They would then create an angled or oblique formation, refuse the weakened flank and attack the strongest flank of the enemy with a concentration of force. Once the critical flank was secure, the commander would wheel the troops 90 degrees to roll up the enemy line, and the angled formation would continue to advance. The echelons not involved in the assault served the important function of holding the rival army in check by remaining defensive and threatening, thus offering protection to the attacking echelons by keeping the enemy force occupied. On occasion both commanders would attempt the same tactic (e.g.the Diadochi trying to replicate Alexander's tactics).

There were some dangers with attempting an oblique order in battle, namely the chance of opening up a fatal gap between the two wings, or that the two forces may completely lose contact. Moreover, the Frederician oblique order called for a long march, either through the night, or in the early hours of the morning of the assault, which meant that the advancing Prussian forces were almost always fatigued by the time they engaged their enemy. Another risky aspect of the oblique order was that it required total determination, as, once it was executed, the assaulting echelons would be deployed with no chance of being recalled.

Proper execution of Frederick’s oblique order involved three main requirements. First, each officer needed to know exactly how to form a battalion from "line to column, maintain its place in the column, and then redeploy either normally, or en echelon for the final attack." The next two necessities were that the soldiers marched in close formation, and in step. Cadenced marching had not been used since the days of the Roman Empire; however, uncadenced marching, or 'route step', required loose marching order to ensure that the soldiers did not bump into each other, and the oblique order could not have been implemented in such unstructured formations. Lastly, for the oblique order to be successful the leaders of the opposing forces had to be unaware of the Frederician technique, which could be countered by a quick response from them; the attack required a confused enemy army incapable of a rapid change in their deployment. Frederick's oblique order was born of the desire to overwhelm a weak point in the enemy line, thus allowing a smaller Prussian force superiority on the battlefield.

History
The first recorded use of a tactic similar to the oblique order was at the Battle of Leuctra, in Greece, when the Thebans under Epaminondas defeated the Spartans by highly enforcing one flank to fifty rows deep, rather than spread forces parsimoniously. Philip of Macedon while held prisoner at Thebes would have learnt Epaminondas' technique, and his descendants, including Alexander the Great, used its variations in their campaigns. The classical writer Vegetius was the first known to write about the tactic that became the oblique order of battle. Subsequent military commanders in the early modern world again employed such tactics once they rediscovered the writings of antiquity. Raimondo Montecuccoli, who maintained that the best forces should always be positioned on the flanks with the more powerful wing initiating the attack, was the first of the more modern generals to employ tactics similar to the oblique order of battle, and Frederick II of Prussia was well aware of the texts of Montecuccoli.

Prussian generals under Frederick the Great used the tactic in their own manner. The Prussian attacking army sent a strong advance force of infantry directly towards the enemy. The frontline troops occupied the attention of the enemy and the rest of the troops would maneuver behind it. They could also exploit any locally available obstacle, using hindering terrain or the smoke of cannon and musket fire to mask maneuvers. The Prussian cavalry would be stationed so as to cover the flank of the main body. Frederick even instructed his senior officers that numerical inferiority was indeed an advantage when it came to implementing ‘his oblique order’, as they could merely weaken one wing while reinforcing the other.

The main body of the army would then spread their forces to one side and deploy in an echelon (or the "oblique order"), spreading their firepower and attacking the stronger enemy flank with increasing pressure. The protective cavalry would then exploit any enemy collapse. Frederick first implemented his oblique order at the Battle of Hohenfriedberg, in 1745, with a subsequent major victory, despite numerical inferiority, at the Battle of Leuthen in 1757. It was this decade between the Silesian Wars and the Seven Years War that Frederick had his army perfect all the manoeuvres of the oblique order of battle.

The theoretical seeds of Frederick’s oblique order can be seen in two of the Seelowitz Instructions’ (‘Instruction für die Cavalleire’, 17 March, Oeuvres, XXX, 33; ‘Disposition für die sämmtlichen Regimenter Infanterie’, 25 March Oeuvres, XXX, 75) in March 1742. Members of the German General Staff maintained that Frederick was only dedicated to the oblique order after the Second Silesian War, with full-hearted application of the tactic in the Seven Years war; however, Otto Herrman disputed the Staff Historians’ insubstantial definitions of oblique order and claimed that Frederick had sought to utilize oblique at Mollwitz and Chotusitz. The most likely and poignant arguments for the advent of Fredrician oblique order came from Rudolf Keibel, who held that Frederick had indeed been implementing it since Hohenfriedberg.

Since the Austrians had been taught valuable lessons in the Wars for Silesia, Frederician tactics were, as Frederick knew from his informants, a subject of discussion in the Viennese cabinet, where Francis I Holy Roman Emperor remarked that ‘Old Fritz’ preferred a one-winged-attack style of warfare that burdened his troops heavily. Then, in 1760, official documents obtained in the capture of Major-General Gzetttritz offered direct insight to the Frederick’s oblique tactics, meaning that Frederick could henceforth be engaged with a well-informed army capable of countering his tactics. Furthermore, the Prussian forces, being heavily fatigued by the time they reached their target, lacked the ability to repel a well-situated enemy, such as at Kunersdorf, or an enemy that made a sudden about-turn, such as at the Battle of Zorndorf or the Battle of Torgau.