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).