Interior lines

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Interior lines[a] (as opposed to exterior lines) is a military term, derived from the generic term line of operation or line of movement.[1] The term "interior lines" is commonly used to illustrate, describe, and analyze the various possible routes (lines) of logistics, supply, recon, approach, attack, evasion, maneuver, or retreat of armed forces. Interior line strategies are based on the fact that lines of movement and communication within an enclosed area are shorter and safer than those on the outside. As the area held by a defensive force shrinks, the interior line advantage held by the defensive force increases.[2][3]

Skillful and comprehensive application of interior line tactics can for a partially surrounded, hard pressed combat force provide vital breathing space, greatly reduce time, effort, security, and secrecy of resupplies and redeployment, and decrease the number of casualties. These effects may have a great impact on morale and eventually prove decisive, as according to Napoleon Bonaparte: "in war morale forces are to physical three to one".[4][5]


By September 1950, US and South Korean Forces had been forced back to form the Pusan Perimeter in the South-East of the peninsula, giving the defenders shorter interior lines. This created a concentration of forces in defense, allowing quicker reinforcements and logistics. Fresh troops and supplies were increasingly being brought into the port in Pusan, strengthening the defense even further and preventing a North Korean victory. By contrast, the North Korean supply line had lengthened, making offensive action harder to maintain. See also Battle of Pusan Perimeter logistics.
Abstract Depiction of the advantages of interior lines in the scenario of battle field tactics.

In the context of battlefield tactics, interior lines allow for more rapid concentration of resources (firepower and manpower) and afford greater tactical flexibility. Resources are ideally brought to bear at a point where the adversary is not able to quickly respond, because of their longer external lines. Examples include:


As a strategy, interior lines are commonly employed to cut armies off from reinforcements and supplies, or prevent allies from uniting their forces. Interior lines often allow for a numerically inferior force to gain a numerical superiority over an adversary in a given locality, which increases the chances of overpowering an enemy and defeating it in detail. In overpowering an enemy locally, an army hopes to demoralize the enemy sufficiently bring it to political terms.

Some examples include:

Montenotte Campaign, Battle of Mondovì, 21 April 1796
After the Battle of Mondovi, the French gained the advantage of having the interior position over their adversaries in the First Coalition.

See also[edit]


  1. ^ a term invented by 19th century Swiss-French officer and prominent author Antoine-Henri Jomini


  1. ^ Michael D. Lundy (December 6, 2017). "Operations, chapter 5 - Passage of lines" (PDF). US Army. Retrieved May 4, 2020.
  2. ^ William O'Connor Morris (1895). Moltke a biographical and critical study. Рипол Классик. pp. 85–. ISBN 978-5-87074-092-8.
  3. ^ Alfred Higgins Burne (1946). Strategy as Exemplified in the Second World War: A Strategical Examination of the Land Operations. CUP Archive. pp. 17–. GGKEY:7F20S7AZG5P.
  4. ^ A General Biographical Dictionary: Comprising a Summary Account of the Most Distinguished Persons of All Ages, Nations, and Professions, Including More Than One Thousand Articles of American Biography ... A.V. Blake. 1845. pp. 1001–.
  5. ^ David T. Zabecki (27 September 2006). The German 1918 Offensives: A Case Study in The Operational Level of War. Routledge. pp. 66–. ISBN 978-1-134-25224-4.
  6. ^ Kent Masterson Brown, Esq. (1 August 2011). Retreat from Gettysburg: Lee, Logistics, and the Pennsylvania Campaign. UNC Press Books. pp. 44–. ISBN 978-0-8078-6942-0.
  7. ^ Kevin Dougherty (6 March 2015). The Vicksburg Campaign: Strategy, Battles and Key Figures. McFarland. pp. 107–. ISBN 978-1-4766-1993-4.