diff --git a/app/game-engine/src/turn/frontStateHandler.ts b/app/game-engine/src/turn/frontStateHandler.ts
new file mode 100644
index 0000000..a967db0
--- /dev/null
+++ b/app/game-engine/src/turn/frontStateHandler.ts
@@ -0,0 +1,164 @@
+import type { City, MapDefinition, Nation } from '@sammo-ts/logic';
+import type { InMemoryTurnWorld, TurnCalendarHandler } from './inMemoryWorld.js';
+import type { TurnDiplomacy } from './types.js';
+
+type ConnectionMap = Map<number, number[]>;
+
+const buildConnectionMap = (map: MapDefinition): ConnectionMap => {
+    const connectionMap = new Map<number, number[]>();
+    for (const city of map.cities) {
+        connectionMap.set(city.id, city.connections ?? []);
+    }
+    return connectionMap;
+};
+
+const collectAdjacentCities = (cityIds: number[], connectionMap: ConnectionMap, bucket: Set<number>): void => {
+    for (const cityId of cityIds) {
+        const neighbors = connectionMap.get(cityId) ?? [];
+        for (const neighborId of neighbors) {
+            bucket.add(neighborId);
+        }
+    }
+};
+
+const collectNationCityIds = (cities: City[]): Map<number, number[]> => {
+    const map = new Map<number, number[]>();
+    for (const city of cities) {
+        const list = map.get(city.nationId) ?? [];
+        list.push(city.id);
+        map.set(city.nationId, list);
+    }
+    return map;
+};
+
+const collectDiplomacyTargets = (entries: TurnDiplomacy[], nationId: number): {
+    warTargets: number[];
+    declareTargets: number[];
+} => {
+    const warTargets: number[] = [];
+    const declareTargets: number[] = [];
+    for (const entry of entries) {
+        if (entry.fromNationId !== nationId) {
+            continue;
+        }
+        if (entry.state === 0) {
+            warTargets.push(entry.toNationId);
+        } else if (entry.state === 1 && entry.term <= 5) {
+            declareTargets.push(entry.toNationId);
+        }
+    }
+    return { warTargets, declareTargets };
+};
+
+const resolveNationFrontStates = (
+    nationId: number,
+    connectionMap: ConnectionMap,
+    cityIdsByNation: Map<number, number[]>,
+    diplomacy: TurnDiplomacy[]
+): Map<number, number> => {
+    const frontStates = new Map<number, number>();
+    if (nationId <= 0) {
+        return frontStates;
+    }
+
+    const { warTargets, declareTargets } = collectDiplomacyTargets(diplomacy, nationId);
+    const adj3 = new Set<number>();
+    const adj2 = new Set<number>();
+    const adj1 = new Set<number>();
+
+    for (const targetNationId of warTargets) {
+        const targetCities = cityIdsByNation.get(targetNationId) ?? [];
+        collectAdjacentCities(targetCities, connectionMap, adj3);
+    }
+
+    for (const targetNationId of declareTargets) {
+        const targetCities = cityIdsByNation.get(targetNationId) ?? [];
+        collectAdjacentCities(targetCities, connectionMap, adj1);
+    }
+
+    if (adj3.size === 0 && adj1.size === 0) {
+        const neutralCities = cityIdsByNation.get(0) ?? [];
+        collectAdjacentCities(neutralCities, connectionMap, adj2);
+    }
+
+    const nationCityIds = cityIdsByNation.get(nationId) ?? [];
+    for (const cityId of nationCityIds) {
+        let nextFrontState = 0;
+        if (adj1.has(cityId)) {
+            nextFrontState = 1;
+        }
+        if (adj2.has(cityId)) {
+            nextFrontState = 2;
+        }
+        if (adj3.has(cityId)) {
+            nextFrontState = 3;
+        }
+        frontStates.set(cityId, nextFrontState);
+    }
+    return frontStates;
+};
+
+export const buildFrontStatePatches = (options: {
+    worldView: {
+        listCities(): City[];
+        listNations(): Nation[];
+        listDiplomacy(): TurnDiplomacy[];
+    };
+    map: MapDefinition | null | undefined;
+    nationIds?: number[];
+}): Array<{ id: number; patch: Partial<City> }> => {
+    if (!options.map) {
+        return [];
+    }
+    const connectionMap = buildConnectionMap(options.map);
+    if (connectionMap.size === 0) {
+        return [];
+    }
+    const cities = options.worldView.listCities();
+    const cityIdsByNation = collectNationCityIds(cities);
+    const diplomacy = options.worldView.listDiplomacy();
+    const cityMap = new Map<number, City>();
+    for (const city of cities) {
+        cityMap.set(city.id, city);
+    }
+
+    const nationList = options.nationIds
+        ? options.worldView
+              .listNations()
+              .filter((nation) => options.nationIds?.includes(nation.id))
+        : options.worldView.listNations();
+    const nations = nationList.filter((nation) => nation.level > 0 && nation.capitalCityId);
+    const patches: Array<{ id: number; patch: Partial<City> }> = [];
+    for (const nation of nations) {
+        const frontStates = resolveNationFrontStates(nation.id, connectionMap, cityIdsByNation, diplomacy);
+        for (const [cityId, nextFrontState] of frontStates) {
+            const city = cityMap.get(cityId);
+            if (!city || city.frontState === nextFrontState) {
+                continue;
+            }
+            patches.push({ id: cityId, patch: { frontState: nextFrontState } });
+        }
+    }
+    return patches;
+};
+
+export const createFrontStateHandler = (options: {
+    getWorld: () => InMemoryTurnWorld | null;
+    map: MapDefinition | null | undefined;
+}): TurnCalendarHandler => {
+    return {
+        onMonthChanged: () => {
+            const world = options.getWorld();
+            if (!world) {
+                return;
+            }
+            const patches = buildFrontStatePatches({
+                worldView: world,
+                map: options.map,
+            });
+            for (const patch of patches) {
+                world.updateCity(patch.id, patch.patch);
+            }
+        },
+    };
+};
diff --git a/app/game-engine/src/turn/reservedTurnHandler.ts b/app/game-engine/src/turn/reservedTurnHandler.ts
index 3ce8079..526db46 100644
--- a/app/game-engine/src/turn/reservedTurnHandler.ts
+++ b/app/game-engine/src/turn/reservedTurnHandler.ts
@@ -37,6 +37,7 @@ import {
     type DiplomacyPatch,
 } from '@sammo-ts/logic';
 import { buildCommandEnv, buildReservedTurnDefinitions } from './reservedTurnCommands.js';
+import { buildFrontStatePatches } from './frontStateHandler.js';
 import { buildActionContext } from './reservedTurnActionContext.js';
 import { GeneralAI, shouldUseAi } from './ai/generalAi.js';
 import type { AiReservedTurnProvider } from './ai/types.js';
@@ -701,6 +702,31 @@ export const createReservedTurnHandler = async (options: {
                     }
                 }
 
+                const hasDiplomacyChange = diplomacyPatches.length > 0;
+                const hasNationChange = (resolution.patches?.cities ?? []).some((patch) =>
+                    Object.prototype.hasOwnProperty.call(patch.patch ?? {}, 'nationId')
+                );
+                if (hasDiplomacyChange || hasNationChange) {
+                    const worldView = worldOverlay?.view ?? worldRef;
+                    if (worldView && options.map) {
+                        const frontPatches = buildFrontStatePatches({
+                            worldView,
+                            map: options.map,
+                        });
+                        if (frontPatches.length > 0) {
+                            for (const patch of frontPatches) {
+                                const existing = patches.cities.find((entry) => entry.id === patch.id);
+                                if (existing) {
+                                    existing.patch = { ...existing.patch, ...patch.patch };
+                                } else {
+                                    patches.cities.push({ id: patch.id, patch: patch.patch });
+                                }
+                                worldOverlay?.applyCityPatch(patch.id, patch.patch);
+                            }
+                        }
+                    }
+                }
+
                 return { nextTurnAt: applyNextTurnAt ? resolution.nextTurnAt : undefined, actionKey, usedFallback, blockedReason };
             };
 
diff --git a/app/game-engine/src/turn/turnDaemon.ts b/app/game-engine/src/turn/turnDaemon.ts
index b93c20d..4360e6c 100644
--- a/app/game-engine/src/turn/turnDaemon.ts
+++ b/app/game-engine/src/turn/turnDaemon.ts
@@ -19,6 +19,7 @@ import { createGatewayAdminActionConsumer } from './gatewayAdminActions.js';
 import { createGatewayProfileGate } from './gatewayProfileGate.js';
 import { composeCalendarHandlers } from './calendarHandlers.js';
 import { createIncomeHandler } from './incomeHandler.js';
+import { createFrontStateHandler } from './frontStateHandler.js';
 import { createReservedTurnHandler } from './reservedTurnHandler.js';
 import { createReservedTurnStore } from './reservedTurnStore.js';
 import { createTurnDaemonCommandHandler } from './worldCommandHandler.js';
@@ -122,6 +123,10 @@ export const createTurnDaemonRuntime = async (options: TurnDaemonRuntimeOptions)
         scenarioConfig: snapshot.scenarioConfig,
         nationTraits: nationTraitMap,
     });
+    const frontStateHandler = createFrontStateHandler({
+        getWorld: () => worldRef,
+        map: snapshot.map ?? null,
+    });
     const tournamentAutoStartHandler = createTournamentAutoStartHandler({
         profileName: options.profileName ?? options.profile,
         getRedisClient: () => redisConnector?.client,
@@ -131,6 +136,7 @@ export const createTurnDaemonRuntime = async (options: TurnDaemonRuntimeOptions)
     const calendarHandler = composeCalendarHandlers(
         options.calendarHandler ?? unification?.handler,
         incomeHandler,
+        frontStateHandler,
         tournamentAutoStartHandler
     );
     const worldOptions: InMemoryTurnWorldOptions = {
diff --git a/app/game-engine/test/npcNationGrowthScenario.test.ts b/app/game-engine/test/npcNationGrowthScenario.test.ts
index 83604e0..9615480 100644
--- a/app/game-engine/test/npcNationGrowthScenario.test.ts
+++ b/app/game-engine/test/npcNationGrowthScenario.test.ts
@@ -10,6 +10,7 @@ import { createReservedTurnHandler } from '../src/turn/reservedTurnHandler.js';
 import { InMemoryTurnProcessor } from '../src/turn/inMemoryTurnProcessor.js';
 import { createIncomeHandler } from '../src/turn/incomeHandler.js';
 import { createNpcTaxHandler } from '../src/turn/npcTaxHandler.js';
+import { createFrontStateHandler } from '../src/turn/frontStateHandler.js';
 import { composeCalendarHandlers } from '../src/turn/calendarHandlers.js';
 import { LARGE_TEST_MAP, buildLargeTestCities } from './fixtures/largeTestMap.js';
 
@@ -272,7 +273,12 @@ describe('NPC 대형 시뮬레이션', () => {
             getWorld: () => wrapper.world,
         });
 
-        const calendarHandler = composeCalendarHandlers(incomeHandler, npcTaxHandler);
+        const frontStateHandler = createFrontStateHandler({
+            getWorld: () => wrapper.world,
+            map: LARGE_TEST_MAP,
+        });
+
+        const calendarHandler = composeCalendarHandlers(incomeHandler, npcTaxHandler, frontStateHandler);
 
         const world = new InMemoryTurnWorld(state, snapshot, {
             schedule,