Siege Combat and Engines

Alacrity Fantasy, A TTRPG by Adam J.. McKee and James G. Walker, Jr.

Large-scale conflicts often involve assaulting or defending fortified positions like castles, city walls, or gatehouses, as well as naval battles featuring large vessels. Overcoming these durable defenses typically requires specialized siege engines – powerful machines designed to breach walls, sink ships, destroy battlements, or deliver troops over defenses. These engines operate on a different scale than personal weapons.

Operating Siege Engines

Unlike standard weapons, siege engines require coordinated effort and specialized knowledge:

  • Crew: Each engine lists a minimum crew required for operation. Lacking sufficient crew significantly increases the time needed for actions or makes operation impossible.
  • Actions: Operating a siege engine involves distinct Declared Actions, often performed over multiple rounds.
    • Load: Preparing the ammunition and tensioning/setting the machine. This can take one or more Declared Actions, sometimes by multiple crew members working together.
    • Aim: Adjusting the engine’s trajectory. This typically requires 1 Declared Action and an Engineering skill roll by the crew leader or designated aimer.
    • Fire: Releasing the stored energy. This typically requires 1 Declared Action and may involve another Engineering skill roll for accuracy, especially for indirect-fire weapons like catapults.
  • Skill Used: The Engineering skill is paramount for effectively aiming and firing complex siege engines, calculating trajectories, and understanding the machine’s mechanics.
  • Firing from Ships: Operating siege engines from the deck of a moving vessel is significantly more difficult than from stable ground due to the pitch and roll of the ship. All Engineering checks made to Aim or Fire ship-mounted siege engines suffer a minimum Challenging (-10%) difficulty penalty. This penalty increases to Hard (-20%) or worse in rough seas or during complex ship maneuvers (GM discretion).

Targeting with Siege Engines

  • Structures and Vessels: Siege engines excel at damaging large, stationary or slow-moving targets like walls, gates, towers, and ship hulls. Attacks are made against the target section using the rules for damaging durable targets (see below).
  • Creatures/Units: Siege weapons can target individuals or groups, though often inaccurately. Direct fire weapons (like Ballistae) make an Engineering roll contested by the target’s Dodge skill, with appropriate modifiers. Indirect fire weapons (Catapults/Trebuchets) target a point; the GM determines scatter on a miss (e.g., 1d10 feet away per 5% margin of failure, in a random direction). Creatures in the impact area suffer effects as described under “Damage vs. Creatures from Siege Engines.”
  • Inaccuracy: Engines, especially indirect-fire ones, are prone to inaccuracy. GMs should apply penalties from the Difficulty Ladder for long range, poor visibility, target movement, or hasty aiming, in addition to any penalty for firing from a ship.

Damage vs. Structures and Vessels

Targets like fortifications and ship hulls possess immense resilience. They use two statistics:

  • Material Soak: A flat number representing the material’s resistance (e.g., Wood 5, Stone 8, Iron 10). This is subtracted from incoming physical damage.
  • Integrity (SI/HI): Functioning like Hit Points, this measures overall structural soundness. Structural Integrity (SI) is for buildings/fortifications; Hull Integrity (HI) is for ships/vehicles. Damage exceeding Material Soak reduces this pool.

Fortifications and large vessels have very high Integrity values, necessitating siege engine damage.
Example Integrity Values: A Thick Stone Wall might have Soak 8, SI 1000+ (per 10-foot section). A Reinforced Castle Gate: Soak 8, SI 500+. A Large Warship (e.g., Galley): Soak 5, HI 240-400+. A Large Merchant Ship (e.g., Cog): Soak 5, HI 160-250+.

Damage Thresholds for Structures/Vessels:

  • Below 50% Max SI/HI: Significant damage is visible. Penalties may apply (e.g., -10% Navigation for ships, structural weakness for walls).
  • Below 25% Max SI/HI: Severely compromised. Penalties worsen. Significant hits risk Critical Damage (GM determines: collapsing section, hull breach/flooding, mast snap, rudder jam, spreading fire, crew panic requiring Command checks).
  • 0 SI/HI or Less: Catastrophic failure. The structure collapses, the ship sinks/breaks apart; it is effectively destroyed.

Damage vs. Creatures from Siege Engines

Being hit by siege weapon ammunition is often instantly lethal.

  • Evasion: Creatures directly targeted or caught in an impact radius can make a Dodge check against Difficulty Hard (-20%).
  • Damage Taken:
    • Failure: Take full siege weapon damage.
    • Success: Take half damage.
    • Critical Success (on Dodge): Take quarter damage (rounded down).
  • GM Note: Even reduced damage is likely extreme. Consider secondary effects like knockback or being knocked prone even on a successful Dodge.

Siege Engine Statistics

Here are statistics for common pre-gunpowder siege engines. Hull Integrity (HI) and Soak for engines represent their own durability.

Ballista (Heavy Crossbow Analogue)
Crew: 3. Actions: Load (1 Declared Action), Aim (1 Declared Action, Engineering Check), Fire (1 Declared Action, Engineering Check). Range: Long+ (e.g., 150-600 ft). Damage: 8d10 Piercing. Area: Single Target. Structure: HI 50, Soak 5 (Wood). Notes: Accurate direct fire. Good against large creatures, gates, enemy engines, or specific structural points.

Mangonel (Catapult / Onager)
Crew: 4. Actions: Load (2 Declared Actions), Aim (1 Declared Action, Engineering Check), Fire (1 Declared Action, Engineering Check). Range: Long (e.g., 100-400 ft). Damage: 10d10 Bludgeoning. Area: 10ft Radius Impact. Structure: HI 75, Soak 5 (Wood/Iron). Notes: Fires heavy stones/projectiles in an arc. Good against structures and troop formations. Prone to inaccuracy (GM determines scatter on miss).

Trebuchet (Counterweight Catapult)
Crew: 5+. Actions: Load (Requires multiple crew over several minutes), Aim (1 Declared Action, Engineering Check), Fire (1 Declared Action, Engineering Check). Range: Extreme (e.g., 300-1000+ ft). Damage: 20d10 Bludgeoning. Area: 15-20ft Radius Impact. Structure: HI 100, Soak 5 (Heavy Wood/Iron). Notes: Massive structure, slow to operate. Devastating against fortifications but highly inaccurate (GM determines scatter). Requires stable ground.

Battering Ram (Medium, Covered)
Crew: 6+ (pushing/swinging). Move: 10 ft/rd (pushed by crew). Action: Ram (1 Declared Action, requires coordinated crew effort – potentially group Athletics check). Range: Melee. Damage: 10d10 Bludgeoning (vs. Structures, ignores Material Soak up to 5). Area: Single Point (Gate/Wall section). Structure: HI 150, Soak 5 (Wood/Hide Cover). Notes: Provides cover for operators. Only effective against gates, doors, or weaker wall sections.

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File Created: 05/06/2025
Last Modified: 05/06/2025

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