The Oblique Order (or declined or refused flank) is a military tactic where 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 allowed 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 the 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, 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 their troops 90 degrees to roll up the enemy line and the angled formation would continue to advance. On occasion both commanders would attempt the same tactic (e.g.the Diadochi trying to replicate Alexander's tactics).
History
The first recorded use of a tactic similar to the oblique order was at the Battle of Leuctra, when the Thebans under Epaminondas defeated the Spartans. Philip of Macedon studied under Epaminondas, and his descendants, including Alexander the Great, used its variations in their campaigns. 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. 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. This tactic decided the Battle of Leuthen in Frederick's favor.
