Flank (military)

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Flank is used in the military as a tactical term and as a term in fortress construction.


The sides of a troop divided according to the depth (on the march or in combat) are called flanks. Since the bulk of the weapons can only act forward (in the enemy direction), the flanks were and are always particularly at risk. Troops protect themselves against side attacks (flank attacks)

  • Flank protection (forces deployed to the side of the main troops for reconnaissance or surveillance ),
  • Based on natural (mountains, swamps, rivers) or artificial ( mine barriers , fortresses ) obstacles, or through
  • Based on neighboring troops in neighboring sections with which they are in tactical contact.

The special importance of operations against the flank of the enemy results from the possibility of shifting the balance of power extremely in one's own favor.

Flank attack functional principle

Fictional example

An army of 10,000 men is attacked by 2,000 men in the flank. Both armies are set up according to the principles of linear tactics . The first meeting of three members , each one meter apart, is followed by a second meeting, which is also set up, 100 meters away. The space in between is covered on the sides by a likewise three-part column as flank protection. The 10,000 man army has a depth of about 110 meters and a width of about 1,300 meters (1 man 0.5 m deep, 0.8 m wide). The attacking 2,000-man army has a width of about 210 meters at the same depth (because it is set up in the same way). Since the battle only takes place on the flank of the larger army, apart from its flank security (approx. 200 men), only a few soldiers from the attacked wing can be deployed for defense, the rest must first be marched there. The attacker can, however, immediately use his first meeting (approx. 800 men) fully and effectively. The overall balance of forces of 5: 1 against him has thus changed at the scene of the battle to a ratio of 4: 1 in his favor. If everything goes well, the weaker army can smash the enemy forces standing in front of it before new forces are brought in and thus maintain their local superiority. In that case, she would roll up the enemy from the flank .

For this reason, in almost the entire history of war there is an effort to win the flank from the enemy and to hit him there. In order to prevent this, the movements of the opponent were always explained as comprehensively as possible and, if necessary, the own front was rotated with the movements of the opponent.

As an alternative, the aim was to break through the enemy front and then attack either against the rear or the two newly created flanks (lying in the front) and then roll up the enemy on both sides.


Battle of Leuthen: The Austrians (red) have bent their left wing backwards to protect the flank. The Prussian Army (blue) is attacking this flank and has set up troops on the sides to protect its own flank between their meetings

In ancient times, the flanks were usually not secured separately during battle. The cavalry initially stood on the wings and thus had to take over the flanks and their protection, but then mostly led their own fight against the enemy cavalry. The task of the generals was to set up the troops in such a way that the enemy could not outflank them and thereby get into the flank. During the marches, the cavalry took over the security of the flanks until the late modern era (sometimes even during the Second World War ).

The crooked order of battle , in which one wing of the army is massively reinforced at the expense of the other , proved to be an effective means of making a flank attack possible . With the help of this tactic, the Battle of Leuktra in 371 BC In the conflict between Sparta and Thebes , as well as the battle of Issus by Alexander the Great and the battle of Pharsalus by Caesar. The battle of Leuthen is one of the few battles in which the flank was actually attacked directly (apart from attacks on marching armies) .

With the advent of linear tactics, the thin lines forced the formation of at least one further line (second meeting), which followed the previous one and had to fill any gaps that had arisen. The lateral gap between the lines (the flank) has since been covered by troops specially posted on the edges of the line for this purpose. However, linear tactics were no more vulnerable to flank attacks than troops are today. In the column tactics of the early 19th century, the flanks were mostly protected by backward-staggered units, which could be brought up quickly in the event of a threat, but otherwise remained available as a reserve. At the Battle of Waterloo , Napoleon had used most of his reserves when the Prussians appeared on his right flank. In the battle of Königgrätz , Moltke only united his armies on the battlefield. When the Prussian 2nd Army appeared on the right wing and on the flank of the Austrians, the battle for Prussia was won.

Another classic example of flank attacks is the Battle of Chancellorsville in the American Civil War .

In the period up to the First World War , the flank attack dominated the tactical thinking of the German General Staff. The continuous western front of the First World War offered the enemy no flanks after the race to the sea , as the armies fought against the Channel coast or the Alps (and neutral Switzerland). On the eastern and southern fronts, however, operations were carried out against the flanks as far as possible. The 12th Isonzo Battle can be regarded as the largest such operation, in which the flank was won over the weak left wing of the Italian 2nd Army. The occupation of Norway and Greece in World War II, which were supposed to cover the strategic flank of the German Reich and its Russian campaign , can serve as an example of strategic flank operations .

Fortress construction

In fortress construction , flanks are those lines of a cover that line the length of the immediate area in front of another line of defense (flank).

In the case of individual independent fortifications , such as lunettes and semi-curbs , those two lines are called flanks that are intended to line the lateral terrain and to flank neighboring structures and the spaces in between. In the case of fortification walls, the flanks are mainly used to coat the length of the fortress moats, they appear here as open ramparts or as casemated flanks.

In bastion plan the bastion flanks the main trench from the center of a suitable arrangement of the front curtain wall flank to the tip of the side Bastion. The bastion flanks were originally placed perpendicular to the curtain wall (Italian building school), later (according to Daniel Specklin ) they were moved to a position perpendicular to the defense lines, which enabled better flanking to be achieved.

See also: Technical terms fortress construction


  • Ulrich Steindorff (Hrsg.): War pocket book - a reference dictionary about the world war , Leipzig and Berlin 1916