Flanking Maneuver

The flank movement is a offensive military tactic that seeks to circumvent the wings of the enemy positions attacking its flanks (sides) or the rear.

Advantages
Some of the possibilities offered by flank movement are: Assaulting enemy positions laterally, the attacker opens the possibility of using Enfilade Fire and Roll the Flank of the defender.
 * avoid the enemy's main defenses.
 * opportunity to concentrate their forces only on the fraction of enemy troops on the flank that is attacked.
 * possibility of a surprise tactic.
 * possibility of isolating the enemy from their rear, disrupting their lines of communications and the influx of supplies and reinforcements.
 * possibility of cutting the routes of withdrawal of the enemy, preventing this leak.

Risks
If there is balance of power, the flank movement is a tactical option that is risky for the attacker. To avoid exposure of his own rear and not to reveal his intentions, the attacker is usually obliged to divide his forces, using a part in the flank movement, while another remains blocking the front of the opponent. This is contrary to the principle of concentration of forces, Giving a well-prepared enemy the chance to tackle each group separately.

Additionally, the troops employed in the flank movement are forced to separate from its own rear, at the risk of having their lines of retreat blocked.

Measures for Protection against Flank Maneuver
Military commanders have some preventive measures that can prevent or decrease the effectiveness of a flank attack. These include: Once through the flank under attack, the commander defender has several tactical options. Some of them are:
 * Establish observation posts and launch Patrols to receive timely warning of the attack.
 * "Anchor " on the flanks of natural barriers like mountains and rivers. The job of the attacker will be much harder if you have to make the assault up the mountain or across a watercourse.
 * Keep troops Reserve rear, ready to reinforce the flank attack.
 * Arrange the defenses in depth, and not all placed in one line.
 * Prepare secondary defensive positions behind the main lines of defense, which can retreat to if the main defenses can not be sustained.
 * Prepare defensive positions on the side of the wings, to address the specific flanking.
 * Simply allocate more troops and weapons to the flanks.
 * change partially or entirely from the front, turning in the direction of the attack. This maneuver is known as refuse the flank".
 * reinforce the flank attack, using reserve troops or parties that are not being attacked.
 * retreat across the defensive line to secondary positions, behind the main. Further , one might be tempted counterattack.

Battles won by using flanking maneuvers

 * Battle of Aljubarrota
 * Battle of Gaugamela