PHASES IN

Phases of Prolonged Medieval Siege Warfare (Attack, Defense, & Counter-Offensive)

A medieval castle siege was rarely a single violent clash; it was a slow, methodical game of attrition, engineering, and psychological warfare. When defensive walls were too thick to breach quickly and immediate assault meant slaughter, the operation shifted into a prolonged siege.

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Phase 1: Investment & Containment (Establishment)

The primary goal of the initial phase was to seal the garrison inside and cut off all external relief or supply lines.

• Castle Attack (Attacker):
  • Encirclement & Lines of Contravallation: The besieging army constructed outer defensive walls, ditches, or palisades facing the castle (contravallation) to prevent sorties by the defenders and stop supplies or messengers from getting in.
  • Lines of Circumvallation: If a relieving force was expected, an outer ring facing outward (circumvallation) was built to protect the attackers' rear.
  • Camp Construction: Attackers built semi-permanent encampments, establishing supply depots, command tents, and forge sites out of range of defensive archers and siege engines.
• Castle Defense (Defender):
  • Gathering & Rationing: The garrison gathered surrounding livestock, burned crops in nearby fields (scorched earth to starve attackers), and retreated behind the main gate.
  • Sorties (Early Strikes): Small cavalry or infantry raids were launched before encirclement was complete to harass the enemy's vanguard, destroy siege preparation materials, and stall camp setup.
  • Signal Fires & Messengers: Fast riders or signal fires were sent to call upon allied lords or kings for a relief force.

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Phase 2: Reduction & Preparation (Softening the Defenses)

Once the castle was isolated, attackers prepared heavy siege equipment while attempting to destroy defensive structures from a safe distance.

• Castle Attack (Attacker):
  • Artillery Bombardment: Trebuchets, traction trebuchets, and mangonels launched heavy stones to weaken parapets and crenellations, alongside incendiary loads (pitch, fireballs) to ignite wooden structures inside the courtyard (bailey).
  • Psychological & Biological Warfare: Launching severed heads, dead animals, or diseased carcasses into the courtyard to break morale and spread illness.
  • Approach Engineering: Filling moat sections with dirt, debris, or fascines (bundles of sticks) to create stable ground for siege towers (belfries) and battering rams.
• Castle Defense (Defender):
  • Counter-Battery Fire: Castle-mounted catapults, ballistas, and springalds targeted enemy siege engine construction sites and crew personnel.
  • Archery & Crossbow Suppression: Longbowmen and crossbowmen positioned along hoardings or arrow slits maintained continuous suppressive fire to stall moat-filling crews.
  • Damping Impact: Hanging wooden beams, wool bales, or sacks of straw over wall faces to absorb stone impacts from enemy trebuchets.

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Phase 3: Breach Operations & Sappers (Breaking the Wall)

If bombardment failed to collapse thick stone curtain walls, the fight moved underground or directly to the base of the fortifications.

• Castle Attack (Attacker):
  • Sapping / Undermining: Digging tunnels underneath the curtain wall or corner towers. Once beneath the foundation, the tunnel was held up with wooden props, filled with combustibles (often pig fat and brushwood), and set on fire to collapse the masonry above.
  • Battering Rams: Protected under heavy wooden shelters called "cats" or "tortoises," soldiers advanced to pound away at gates, postern doors, or weakened masonry.
  • Siege Towers (Belfries): Rolling massive multi-story wooden towers up to the wall face to lower drawbridges for assault troops.
• Castle Defense (Defender):
  • Counter-Mining: Digging counter-tunnels to intercept enemy sappers underground, leading to brutal, pitch-black close-quarters hand-to-hand combat beneath the earth.
  • Preventing Wall Impact: Dropping heavy weight bundles or chains to catch and deflect battering ram heads.
  • Defensive Drop Hazards: Pouring boiling water, hot sand, burning pitch, or quicklime down through machicolations (wall overhang apertures) onto rams and sappers working at the base.

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Phase 4: Attrition, Sickness & Negotiation (The Waiting Game)

When physical breaches proved too difficult or costly, prolonged sieges turned into grueling endurance tests where disease and starvation were the primary weapons.

• Castle Attack (Attacker):
  • Enforcing Starvation: Waiting out the defenders until food and clean water supplies ran out.
  • Managing Camp Hygiene: Managing dysentery, cholera, and typhus within the besieging camp—often the attacker suffered higher disease casualties than the defender due to poor sanitation in stagnant encampments.
  • Parley & Terms: Offering conditional surrender terms (e.g., safe passage or sparing of lives) to encourage the garrison to yield before a final bloody assault.
• Castle Defense (Defender):
  • Strict Rationing: Expelling "useless mouths" (non-combatant civilians, elderly, or wounded) outside the gates to preserve food for soldiers—though attackers often drove them back to force the garrison's hand.
  • Water Management: Securing deep cisterns and wells, while rationing fresh water strictly.
  • Pact of Conditional Surrender: Agreeing to surrender if an allied relief army did not arrive within a specified timeframe (e.g., 40 days).

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Phase 5: The Final Assault & Resolution

A siege ended in one of three primary ways inside or around the walls: surrender by terms, a brutal final storming of breached walls, or the arrival of a relieving army.

• Outcome A: Conditional Surrender (Most Common)
  If no relief force arrived and food was exhausted, the castle commander negotiated terms, surrendering the keys in exchange for the garrison's life, arms, or freedom.
• Outcome B: The Storming (Breach & Fall)
  If the garrison refused terms and a breach was made, attackers launched a total assault. Under medieval customary law of war (jus in bello), if a castle forced a full storming, attackers were entitled to loot the stronghold and show no quarter to the survivors.
• Outcome C: Lifting the Siege
  The attackers were forced to retreat due to an incoming relieving army, harsh winter conditions, logistics collapse, or devastating disease outbreaks in their camp.

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Phase 6: Chasing-Back the Run-Away Attacker (The Counter-Offensive & Pursuit)

A medieval siege did not always conclude neat and cleanly inside the castle walls. When an attacking force collapsed—whether broken by an incoming relief army, devastated by disease, or defeated during a failed final assault—the tactical dynamic reversed completely. The besieged garrison shifted from defensive endurance to aggressive pursuit to annihilate the fleeing enemy, capture high-value war gear, and prevent them from regrouping.

• Castle Defense (Now the Pursuer):
  • Exploiting the Breaking Point: The moment enemy lines wavered—triggered by the sight of a relieving army's vanguard or a disastrous failed breach—the garrison threw open the main gates or postern doors to launch a full-scale sortie (sally).
  • Cavalry Harassment & Flanking: Mounted knights and light cavalry rushed out to cut off retreat corridors, striking the fleeing enemy's rear guard and baggage trains where organization was weakest.
  • Destruction of Siege Engines: Fast-moving infantry squads targeted abandoned trebuchets, siege towers, and sapping equipment, setting them ablaze with pitch to ensure they could not be reused in a future campaign.
  • Capturing High-Value Assets: Pursuing forces prioritized capturing noble commanders for ransom, seizing supply wagons, looting armories, and taking control of intact siege artillery left behind in camp.
• Castle Attack (Now the Fleeing Force):
  • Fighting Rear-Guard Actions: To buy time for the main body and supply lines to escape, a dedicated rear guard (often heavy infantry or dismounted cavalry) was left behind to hold narrow chokepoints, bridge crossings, or outer earthworks.
  • Scorched Camp Abandonment: Retreating troops set fire to their own tents, supply depots, and unmovable siege engines to prevent valuable equipment and food from falling into the hands of the garrison.
  • Sustaining Route Casualties: Depleted by disease, hunger, and low morale from a failed siege, retreating soldiers faced extreme mortality rates during the pursuit phase, often losing more men in the rout than during active bombardment.

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Tactical Resolution Flowchart

graph TD SR[SIEGE RESOLUTION] --> A[SURRENDER] SR --> B[ASSAULT] SR --> C[RELIEF] SR --> D[PURSUIT & COUNTER-ATTACK] A --> A1[Terms of Accord] A --> A2[Garrison Vacates] B --> B1[Breach Assault] B --> B2[Looting & Fall] C --> C1[Relieving Army Arrives] C --> C2[Attacker Lifts Siege] D --> D1[Garrison Sally Out] D --> D2[Cavalry Harasses Rear] D --> D3[Capture of Camp & Gear]