diff --git a/src/Domain/MatchState.php b/src/Domain/MatchState.php
index 5e2e6f8..06bf1dc 100644
--- a/src/Domain/MatchState.php
+++ b/src/Domain/MatchState.php
@@ -11,6 +11,8 @@ final readonly class MatchState
     /**
      * @param list<UnitState> $units
      * @param list<string> $actionLog
+     * @param array<string, ObjectiveMarker> $objectives
+     * @param array<string, int> $objectiveControl
      */
     public function __construct(
         public Battlefield $battlefield,
@@ -19,6 +21,10 @@ final readonly class MatchState
         public int $round = 1,
         public ?string $winnerTeamId = null,
         public array $actionLog = [],
+        public array $objectives = [],
+        public VictoryCondition $victoryCondition = VictoryCondition::EliminateAll,
+        public int $holdRoundsRequired = 1,
+        public array $objectiveControl = [],
     ) {
         if (!self::isList($units)) {
             throw new InvalidArgumentException('Match units must be a list.');
@@ -92,6 +98,28 @@ final readonly class MatchState
         if ($winnerTeamId !== null && !isset($teamIds[$winnerTeamId])) {
             throw new InvalidArgumentException("Winner team has no units: {$winnerTeamId}.");
         }
+
+        if ($holdRoundsRequired < 1) {
+            throw new InvalidArgumentException('Hold rounds required must be at least 1.');
+        }
+
+        foreach ($objectives as $objective) {
+            if (!$objective instanceof ObjectiveMarker) { // @phpstan-ignore instanceof.alwaysTrue (Runtime guard: PHPDoc is not a runtime contract for JSON-sourced arrays in Plan 4.)
+                throw new InvalidArgumentException('Objectives must be ObjectiveMarker instances.');
+            }
+            if (!$battlefield->contains($objective->position)) {
+                throw new InvalidArgumentException("Objective {$objective->id} is outside the battlefield.");
+            }
+        }
+
+        foreach ($objectiveControl as $teamId => $count) {
+            if (!self::isString($teamId) || $teamId === '') {
+                throw new InvalidArgumentException('Objective control team id must be a non-empty string.');
+            }
+            if (!self::isInt($count) || $count < 0) {
+                throw new InvalidArgumentException('Objective control count must be a non-negative integer.');
+            }
+        }
     }
 
     private static function isUnitState(mixed $unit): bool
@@ -104,6 +132,11 @@ final readonly class MatchState
         return is_string($value);
     }
 
+    private static function isInt(mixed $value): bool
+    {
+        return is_int($value);
+    }
+
     private static function isList(mixed $value): bool
     {
         return is_array($value) && array_is_list($value);
@@ -144,18 +177,45 @@ final readonly class MatchState
             $this->round,
             $winnerTeamId,
             $this->actionLog,
+            $this->objectives,
+            $this->victoryCondition,
+            $this->holdRoundsRequired,
+            $this->objectiveControl,
+        );
+    }
+
+    /**
+     * @param array<string, int> $objectiveControl
+     */
+    public function withObjectiveControl(array $objectiveControl): self
+    {
+        return new self(
+            $this->battlefield,
+            $this->units,
+            $this->activeTeamId,
+            $this->round,
+            $this->winnerTeamId,
+            $this->actionLog,
+            $this->objectives,
+            $this->victoryCondition,
+            $this->holdRoundsRequired,
+            $objectiveControl,
         );
     }
 
     /**
      * @param list<UnitState>|null $units
      * @param list<string>|null $actionLog
+     * @param array<string, ObjectiveMarker>|null $objectives
+     * @param array<string, int>|null $objectiveControl
      */
     public function copy(
         ?array $units = null,
         ?string $activeTeamId = null,
         ?int $round = null,
         ?array $actionLog = null,
+        ?array $objectives = null,
+        ?array $objectiveControl = null,
     ): self {
         return new self(
             $this->battlefield,
@@ -164,6 +224,10 @@ final readonly class MatchState
             $round ?? $this->round,
             $this->winnerTeamId,
             $actionLog ?? $this->actionLog,
+            $objectives ?? $this->objectives,
+            $this->victoryCondition,
+            $this->holdRoundsRequired,
+            $objectiveControl ?? $this->objectiveControl,
         );
     }
 }
diff --git a/src/Domain/Scenario.php b/src/Domain/Scenario.php
new file mode 100644
index 0000000..4a3c4ac
--- /dev/null
+++ b/src/Domain/Scenario.php
@@ -0,0 +1,161 @@
+<?php
+
+declare(strict_types=1);
+
+namespace BattleForge\Domain;
+
+use InvalidArgumentException;
+
+final readonly class Scenario
+{
+    /**
+     * @param list<UnitState> $units
+     * @param array<string, DeploymentZone> $deploymentZones
+     * @param array<string, ObjectiveMarker> $objectives
+     */
+    public function __construct(
+        public string $id,
+        public string $name,
+        public Battlefield $battlefield,
+        public array $units,
+        public array $deploymentZones,
+        public array $objectives,
+        public VictoryCondition $victoryCondition,
+        public int $holdRoundsRequired,
+    ) {
+        if ($id === '') {
+            throw new InvalidArgumentException('Scenario id cannot be empty.');
+        }
+
+        if ($name === '') {
+            throw new InvalidArgumentException('Scenario name cannot be empty.');
+        }
+
+        if (!array_is_list($units)) { // @phpstan-ignore function.alreadyNarrowedType (Runtime guard: PHPDoc is not a runtime contract for JSON-sourced arrays in Plan 4.)
+            throw new InvalidArgumentException('Scenario units must be a list.');
+        }
+
+        if ($deploymentZones === []) {
+            throw new InvalidArgumentException('Scenario must declare at least one deployment zone.');
+        }
+
+        if (count($deploymentZones) !== 2) {
+            throw new InvalidArgumentException('Scenarios must declare exactly two deployment zones.');
+        }
+
+        if ($holdRoundsRequired < 1) {
+            throw new InvalidArgumentException('Hold rounds required must be at least 1.');
+        }
+
+        if ($victoryCondition === VictoryCondition::HoldObjective && count($this->objectives) !== 1) {
+            throw new InvalidArgumentException('Hold objective victory requires exactly one objective.');
+        }
+
+        if ($victoryCondition === VictoryCondition::EliminateAll && $this->objectives !== []) {
+            throw new InvalidArgumentException('Eliminate all victory does not allow objectives.');
+        }
+
+        $unitsByTeam = $this->groupUnitsByTeam($units);
+
+        foreach ($unitsByTeam as $teamId => $teamUnits) {
+            if (count($teamUnits) < 3 || count($teamUnits) > 6) {
+                throw new InvalidArgumentException("Team {$teamId} must have between 3 and 6 units.");
+            }
+
+            if (!isset($deploymentZones[$teamId])) {
+                throw new InvalidArgumentException("Team {$teamId} is missing a deployment zone.");
+            }
+        }
+
+        foreach ($units as $unit) {
+            if (!$this->battlefield->contains($unit->position)) {
+                throw new InvalidArgumentException("Unit {$unit->id} is outside the battlefield.");
+            }
+
+            if (!ArchetypeCatalog::templates()[$unit->archetype->value] ?? false) { // @phpstan-ignore nullCoalesce.expr, if.alwaysFalse, booleanNot.alwaysFalse (Runtime guard: defense in depth against an unknown Archetype enum value.)
+                throw new InvalidArgumentException("Unit {$unit->id} uses an unknown archetype.");
+            }
+
+            $template = ArchetypeCatalog::templates()[$unit->archetype->value];
+
+            if ($unit->maxHealth < $template->minHealth || $unit->maxHealth > $template->maxHealth) {
+                throw new InvalidArgumentException("Unit {$unit->id} health is outside archetype bounds.");
+            }
+            if ($unit->attack < $template->minAttack || $unit->attack > $template->maxAttack) {
+                throw new InvalidArgumentException("Unit {$unit->id} attack is outside archetype bounds.");
+            }
+            if ($unit->defense < $template->minDefense || $unit->defense > $template->maxDefense) {
+                throw new InvalidArgumentException("Unit {$unit->id} defense is outside archetype bounds.");
+            }
+            if ($unit->speed < $template->minSpeed || $unit->speed > $template->maxSpeed) {
+                throw new InvalidArgumentException("Unit {$unit->id} speed is outside archetype bounds.");
+            }
+
+            foreach ($unit->abilities as $ability) {
+                if (!in_array($ability, $template->allowedAbilities, true)) {
+                    throw new InvalidArgumentException("Unit {$unit->id} has an ability that its archetype forbids.");
+                }
+            }
+
+            $zone = $deploymentZones[$unit->teamId] ?? null;
+            if ($zone === null || !$zone->contains($unit->position)) {
+                throw new InvalidArgumentException("Unit {$unit->id} must start inside team {$unit->teamId} deployment zone.");
+            }
+        }
+
+        foreach ($objectives as $objective) {
+            if (!$this->battlefield->contains($objective->position)) {
+                throw new InvalidArgumentException("Objective {$objective->id} is outside the battlefield.");
+            }
+        }
+    }
+
+    public function startMatch(string $activeTeamId): MatchState
+    {
+        $resetUnits = [];
+
+        foreach ($this->units as $unit) {
+            $resetUnits[] = new UnitState(
+                $unit->id,
+                $unit->teamId,
+                $unit->position,
+                $unit->maxHealth,
+                $unit->maxHealth,
+                $unit->attack,
+                $unit->defense,
+                $unit->speed,
+                2,
+                false,
+                $unit->archetype,
+                $unit->abilities,
+                0,
+                false,
+            );
+        }
+
+        return new MatchState(
+            battlefield: $this->battlefield,
+            units: $resetUnits,
+            activeTeamId: $activeTeamId,
+            objectives: $this->objectives,
+            victoryCondition: $this->victoryCondition,
+            holdRoundsRequired: $this->holdRoundsRequired,
+        );
+    }
+
+    /**
+     * @param list<UnitState> $units
+     * @return array<string, list<UnitState>>
+     */
+    private function groupUnitsByTeam(array $units): array
+    {
+        $grouped = [];
+
+        foreach ($units as $unit) {
+            $grouped[$unit->teamId] ??= [];
+            $grouped[$unit->teamId][] = $unit;
+        }
+
+        return $grouped;
+    }
+}
diff --git a/tests/Unit/Domain/ScenarioTest.php b/tests/Unit/Domain/ScenarioTest.php
new file mode 100644
index 0000000..18dad5b
--- /dev/null
+++ b/tests/Unit/Domain/ScenarioTest.php
@@ -0,0 +1,245 @@
+<?php
+
+declare(strict_types=1);
+
+namespace BattleForge\Tests\Unit\Domain;
+
+use BattleForge\Domain\Archetype;
+use BattleForge\Domain\Battlefield;
+use BattleForge\Domain\DeploymentZone;
+use BattleForge\Domain\MatchState;
+use BattleForge\Domain\ObjectiveMarker;
+use BattleForge\Domain\Position;
+use BattleForge\Domain\Scenario;
+use BattleForge\Domain\UnitState;
+use BattleForge\Domain\VictoryCondition;
+use InvalidArgumentException;
+use PHPUnit\Framework\TestCase;
+
+final class ScenarioTest extends TestCase
+{
+    public function testItRejectsNonListUnits(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+
+        new Scenario(
+            id: 'demo',
+            name: 'Demo',
+            battlefield: new Battlefield(8, 8),
+            units: ['alpha-1' => $this->unit('alpha-1', 'alpha', new Position(0, 0))], // @phpstan-ignore argument.type (Test fixture intentionally passes a non-list units array to verify constructor validation.)
+            deploymentZones: ['alpha' => new DeploymentZone('alpha', [new Position(0, 0)])],
+            objectives: [],
+            victoryCondition: VictoryCondition::EliminateAll,
+            holdRoundsRequired: 1,
+        );
+    }
+
+    public function testItRejectsTeamsOutsideTheThreeToSixSizeWindow(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('Team alpha must have between 3 and 6 units.');
+
+        $units = [
+            $this->unit('alpha-1', 'alpha', new Position(0, 0)),
+            $this->unit('alpha-2', 'alpha', new Position(1, 0)),
+            $this->unit('bravo-1', 'bravo', new Position(7, 7)),
+            $this->unit('bravo-2', 'bravo', new Position(6, 7)),
+            $this->unit('bravo-3', 'bravo', new Position(5, 7)),
+        ];
+
+        new Scenario(
+            id: 'demo',
+            name: 'Demo',
+            battlefield: new Battlefield(8, 8),
+            units: $units,
+            deploymentZones: [
+                'alpha' => new DeploymentZone('alpha', [new Position(0, 0), new Position(1, 0)]),
+                'bravo' => new DeploymentZone('bravo', [new Position(7, 7), new Position(6, 7), new Position(5, 7)]),
+            ],
+            objectives: [],
+            victoryCondition: VictoryCondition::EliminateAll,
+            holdRoundsRequired: 1,
+        );
+    }
+
+    public function testItRejectsAbilitiesOutsideTheArchetypeAllowlist(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('Unit alpha-1 has an ability that its archetype forbids.');
+
+        $bad = $this->unit('alpha-1', 'alpha', new Position(0, 0), archetype: Archetype::Scout, abilities: ['heal'], attack: 3, defense: 1, speed: 5, maxHealth: 6);
+        $alpha2 = $this->unit('alpha-2', 'alpha', new Position(1, 0));
+        $alpha3 = $this->unit('alpha-3', 'alpha', new Position(2, 0));
+        $bravo = $this->unit('bravo-1', 'bravo', new Position(7, 7));
+        $bravo2 = $this->unit('bravo-2', 'bravo', new Position(6, 7));
+        $bravo3 = $this->unit('bravo-3', 'bravo', new Position(5, 7));
+
+        new Scenario(
+            id: 'demo',
+            name: 'Demo',
+            battlefield: new Battlefield(8, 8),
+            units: [$bad, $alpha2, $alpha3, $bravo, $bravo2, $bravo3],
+            deploymentZones: [
+                'alpha' => new DeploymentZone('alpha', [new Position(0, 0), new Position(1, 0), new Position(2, 0)]),
+                'bravo' => new DeploymentZone('bravo', [new Position(7, 7), new Position(6, 7), new Position(5, 7)]),
+            ],
+            objectives: [],
+            victoryCondition: VictoryCondition::EliminateAll,
+            holdRoundsRequired: 1,
+        );
+    }
+
+    public function testItRejectsUnitsOutsideTheirDeploymentZone(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('Unit alpha-1 must start inside team alpha deployment zone.');
+
+        $bad = $this->unit('alpha-1', 'alpha', new Position(3, 0));
+        $alpha2 = $this->unit('alpha-2', 'alpha', new Position(0, 0));
+        $alpha3 = $this->unit('alpha-3', 'alpha', new Position(1, 0));
+        $bravo = $this->unit('bravo-1', 'bravo', new Position(7, 7));
+        $bravo2 = $this->unit('bravo-2', 'bravo', new Position(6, 7));
+        $bravo3 = $this->unit('bravo-3', 'bravo', new Position(5, 7));
+
+        new Scenario(
+            id: 'demo',
+            name: 'Demo',
+            battlefield: new Battlefield(8, 8),
+            units: [$bad, $alpha2, $alpha3, $bravo, $bravo2, $bravo3],
+            deploymentZones: [
+                'alpha' => new DeploymentZone('alpha', [new Position(0, 0), new Position(1, 0), new Position(2, 0)]),
+                'bravo' => new DeploymentZone('bravo', [new Position(7, 7), new Position(6, 7), new Position(5, 7)]),
+            ],
+            objectives: [],
+            victoryCondition: VictoryCondition::EliminateAll,
+            holdRoundsRequired: 1,
+        );
+    }
+
+    public function testHoldObjectiveRequiresExactlyOneObjective(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('Hold objective victory requires exactly one objective.');
+
+        $units = $this->validUnitSet();
+        $zones = $this->validZones();
+
+        new Scenario(
+            id: 'demo',
+            name: 'Demo',
+            battlefield: new Battlefield(8, 8),
+            units: $units,
+            deploymentZones: $zones,
+            objectives: [],
+            victoryCondition: VictoryCondition::HoldObjective,
+            holdRoundsRequired: 3,
+        );
+    }
+
+    public function testStartMatchReturnsAFreshMatchStateWithResetUnits(): void
+    {
+        $scenario = $this->validScenario();
+
+        $match = $scenario->startMatch('alpha');
+
+        self::assertInstanceOf(MatchState::class, $match);
+        self::assertSame('alpha', $match->activeTeamId);
+        self::assertSame(1, $match->round);
+        self::assertNull($match->winnerTeamId);
+        foreach ($match->units as $unit) {
+            self::assertSame(2, $unit->actionsRemaining);
+            self::assertFalse($unit->hasAttacked);
+            self::assertSame(0, $unit->attackBonus);
+            self::assertFalse($unit->hasUsedAbility);
+        }
+    }
+
+    public function testStartMatchDoesNotShareUnitInstancesWithTheScenario(): void
+    {
+        $scenario = $this->validScenario();
+
+        $match = $scenario->startMatch('alpha');
+
+        $original = $scenario->units[0];
+        $fromMatch = $match->unit($original->id);
+
+        self::assertNotSame($original, $fromMatch);
+        self::assertSame($original->id, $fromMatch->id);
+    }
+
+    /** @return list<UnitState> */
+    private function validUnitSet(): array
+    {
+        return [
+            $this->unit('alpha-1', 'alpha', new Position(0, 0)),
+            $this->unit('alpha-2', 'alpha', new Position(1, 0)),
+            $this->unit('alpha-3', 'alpha', new Position(2, 0)),
+            $this->unit('bravo-1', 'bravo', new Position(7, 7)),
+            $this->unit('bravo-2', 'bravo', new Position(6, 7)),
+            $this->unit('bravo-3', 'bravo', new Position(5, 7)),
+        ];
+    }
+
+    /** @return array<string, DeploymentZone> */
+    private function validZones(): array
+    {
+        return [
+            'alpha' => new DeploymentZone('alpha', [
+                new Position(0, 0),
+                new Position(1, 0),
+                new Position(2, 0),
+            ]),
+            'bravo' => new DeploymentZone('bravo', [
+                new Position(7, 7),
+                new Position(6, 7),
+                new Position(5, 7),
+            ]),
+        ];
+    }
+
+    private function validScenario(): Scenario
+    {
+        return new Scenario(
+            id: 'demo',
+            name: 'Demo',
+            battlefield: new Battlefield(8, 8),
+            units: $this->validUnitSet(),
+            deploymentZones: $this->validZones(),
+            objectives: [],
+            victoryCondition: VictoryCondition::EliminateAll,
+            holdRoundsRequired: 1,
+        );
+    }
+
+    /**
+     * @param list<string> $abilities
+     */
+    private function unit(
+        string $id,
+        string $team,
+        Position $position,
+        Archetype $archetype = Archetype::Defender,
+        array $abilities = [],
+        int $attack = 4,
+        int $defense = 3,
+        int $speed = 3,
+        int $maxHealth = 10,
+    ): UnitState {
+        return new UnitState(
+            $id,
+            $team,
+            $position,
+            $maxHealth,
+            $maxHealth,
+            $attack,
+            $defense,
+            $speed,
+            2,
+            false,
+            $archetype,
+            $abilities,
+            0,
+            false,
+        );
+    }
+}