Battle of Sabis simulation

Battle of Sabis simulation testing outcomes of changes to Caesar's formation type and dispersion level, written with NetLogo 7.

MODEL

• Status

  • Unaware -> Aware time length affected by baggage in LOS (massive baggage trains and lots of dust/debris reported), distance from first aware roman (cavarly was gone, so had to be runners/ word of mouth), or if a Nervii is within LOS
  • Aware -> Orders received time length affected by column compactness (Caesar described great chaos due to legions too close) and a legion leader's time to create orders
    • Legion leader's orders-given time affected by veteran status and whether or not legion was isolated (out of LOS) of others (Legions performed better historically when relatively near each other and not isolated)
  • Orders-received -> Ready time affected by whether or not the legionary was a veteran or rookie

• Combat

  • DPS = (Accuracy of attacker * (1 - Opponent defense) * Lethality of weapon) / attack time avg in seconds
  • Ambush bonus grants Nervii better combat skill if roman is not ready (Caesar's account of how the surprise factor nearly routed them, other accounts of ambushes)
  • If roman is not ready, they can still fight back but their combat skill is greatly diminished
  • If the compactness is very high, combat skill is slightly diminished (Caesar talked about it being so compact that Romans couldn't draw their swords)

ANALYSIS:

Utilized BehaviorSpace in NetLogo to run the following monte-carlo simulations (100 per exp):

Experiments Ran:

• Real life setups:

  1. Caesar's order, Compactness == 1.0 (Caesar's actual order)
  2. Expected order, Compactness == 0.1 (Order the Nervii expected)

• Setups hypothesized to improve conditions for Romans: 3. Caesar's order, Compactness == 0.75 4. Caesar's order, Compactness == 0.6 5. Caesar's order, Compactness == 0.5

• Others to potentially run: 6. Expected order, Compactness == 1.0 7. Caesar's order, Compactness == 0.1 8. Expected order, Compactness == 0.75

RESULTS:

Full CSV results saved as "{formation order}_{compactness}.xlsx" I calculated the averages and std deviations at the bottom of each file.

Reasoning for model choices:

Combat

• Combat skill stochastity: + or - 2.5 points

• Opponent defense stochastity: + or - 5%

• Vet with shortsword: 21

  • Attack time = 2 seconds
  • Accuracy = 0.7
  • Lethality of weapon = 0.6
  • Armor/defense quality = 0.5

• Vet with pilum/javelin: 11.25

  • Attack time = 4 seconds
  • Accuracy = 0.5
  • Lethality = 0.9
  • Armor/defense quality = 0.3 (no shield with pilum)

• Rookie w/ short: 10.5

  • Attack time = 2 seconds
  • Accuracy = 0.35 (half vet)
  • Lethality = 0.6
  • Armor = 0.4 (typically slightly less well equipped than vets)

• Rookie with long: 5.625

  • Attack time= 4 seconds
  • Accuracy = 0.25 (half vet)
  • Lethality = 0.9
  • Armor = 0.2

• Nervii with slashing sword: 12.5

  • Attack time = 2 seconds
  • Accuracy = 0.5 (in between vet and rookie)
  • Lethality = 0.5 (slashing weapons were less lethal than thrusting swords)
  • Armor = 0.1 (only shield if any shield used, no or minimal armor usually)

Lethality

Exact numbers can't be determined, so I use ratios based on qualitative data.

• Nervii: primarily slashing swords of moderate lethality
• Romans: shortswords (highly lethal) and javelins/pilums (also highly lethal)
• Reasoning:
  • Vegetius, De Re Militari (Book 1, Chapter 12). Vegetius states that a slashing blow from a sword "seldom kills." He then contrasts this directly with the Roman gladius: a stab, though it penetrates but two inches, is generally fatal."
    • The weapon is designed for fatal stabs, as cited by Vegetius.
  • Pilum lethality: It was a piece of "personal artillery" designed to punch through a shield and the armor and person behind it. Historian Peter Connolly's tests confirmed it could pierce shields and cause "life-incompatible wounds.
    • Less opponent defense with pilum as they cannot hold shield. less accuracy with pilum.

Accuracy:

• Roman Vet: 0.7 with shortword; 0.5 with javelin.

  • Source: Vegetius, De Re Militari (Book 1)
  • Reasoning: Vegetius describes how Roman recruits were relentlessly drilled. They spent hours striking a wooden post (the palus) as if it were an enemy, practicing their thrusts over and over.

• Nervii Warrior: 0.5 with slashing sword; "Ferocious but less skilled" than a veteran.

  • Source: Julius Caesar, Commentaries on the Gallic War
  • Reasoning: described Nervii as "men of great courage" and the "most warlike" of the Belgae, with a "Spartan-like" culture. furious charge and slashing with longswords. assumption: less precise than a Roman thrust.

• Roman Rookie: 0.35 with shortsword; 0.25 with javelin; half of that of a Roman vet's.

  • Source: Vegetius, De Re Militari (Book 1, Chapter 1): rookies are a liability. "Few men are born brave; many become so through care and force of discipline."
  • Source: Caesar's account of the Sabis (Book 2). In the battle's initial chaos, Caesar notes his rookies panicked and some fled.

Attack time

• Roman shortsword thrust (est 2 seconds) : (Vegetius) roman fighting style was based on a short thrust from behind a shield. This is a very fast and recoverable motion.
• Nervii slashing sword (est 2 seconds): A slashing attack with a longer, heavier sword requires a larger, full-arm or body-rotation movement. est same time as shortsword thrust due to halfhazard nervii "ferocity"
• Pilum: Throw 3 seconds, weapon switch after throwing 1.5 seconds, est 4.5 seconds

Opponent Defense (armor/shields)

• Romans: combination of a large, curved scutum and chain mail (lorica hamata). High defensive value.

  • Source: https://www.thelatinlibrary.com/historians/polyb/polybius5.html (Polybius, Histories (Book 6, Chapter 23).)
  • During initial charge, romans were unprepped, so opponent-defense is mitigated if roman not ready.
  • Romans with pilums couldnt use shields while holding pilum. so opponent defense is mitigated for those holding pilums.

• Nervii: Lower. Occasional flat shield. Body armor was rare and typically reserved for chieftains. The Nervii warrior's defense was almost entirely his shield if he had one.

  • Source for Nervii: Archaeological evidence of little armor, accounts of Caesar in his notes on the Gallic wars.