diff --git a/src/board/OasisRegionPanel.svelte b/src/board/OasisRegionPanel.svelte
index d4bd4cb..4eefeed 100644
--- a/src/board/OasisRegionPanel.svelte
+++ b/src/board/OasisRegionPanel.svelte
@@ -26,6 +26,12 @@
     }
 
 
+    function clear() {
+        if (!region) return;
+        moves.clear(region.id, numberOfUnits);
+    }
+
+
     function toggleMissionRepeat() {
         if (!region) return;
         moves.toggleMissionRepeat(region.id);
@@ -49,14 +55,34 @@
                 <button on:click={ close }>X</button>
             </span>
         </header>
+        { #if region.state.cleared }
+        <p>Region cleared</p>
+        { :else }
+        <p>Defensive strength: { region.strength }</p>
+        { /if }
         { #if region.state.mission }
         <div>
             <p>{ region.state.mission.unitCount } soldiers are on a mission here.</p>
             <p>Remaining: { Math.ceil(region.state.mission.remainingTime / 1000) }</p>
+            { #if region.state.mission.type === 'pillage' }
             <label>
                 <input type="checkbox" checked={ region.state.mission.repeat } on:change={ toggleMissionRepeat }>
                 <span title="Send the same troops again when they come back">Repeat</span>
             </label>
+            { /if }
+        </div>
+        { :else if !region.state.cleared }
+        <div>
+            <input
+                type="range"
+                name="units"
+                min="0"
+                max={ maximumUnits }
+                bind:value={ numberOfUnits }
+            />
+            { numberOfUnits }
+            <button on:click={ setMaxUnits }>↑</button>
+            <button on:click={ clear } disabled={ numberOfUnits === 0 }>Clear</button>
         </div>
         { :else }
         <div>
diff --git a/src/board/Worldmap.svelte b/src/board/Worldmap.svelte
index 1eddf67..5597257 100644
--- a/src/board/Worldmap.svelte
+++ b/src/board/Worldmap.svelte
@@ -16,6 +16,7 @@
         class:empty={ region.type === WORLDMAP_TYPES.EMPTY }
         class:bourgade={ region.type === WORLDMAP_TYPES.BOURGADE }
         class:oasis={ region.type === WORLDMAP_TYPES.OASIS }
+        class:cleared={ region.type === WORLDMAP_TYPES.OASIS && region.state.cleared }
     >
         { #if region.type === WORLDMAP_TYPES.BOURGADE }
         <button class="invisible" on:click={ () => gameTab.set('resources') }>
@@ -63,6 +64,10 @@
     }
 
     .region.oasis {
+        background-color: red;
+    }
+
+    .region.oasis.cleared {
         background-color: cyan;
     }
 </style>
diff --git a/src/missions.ts b/src/missions.ts
index 6bbca31..11b5994 100644
--- a/src/missions.ts
+++ b/src/missions.ts
@@ -17,6 +17,11 @@ export function resolveMission(V: VillageState, region: RegionType) {
                 resolvePillageOasis(V, region);
             }
             break;
+        case 'clear':
+            if (region.type === WORLDMAP_TYPES.OASIS) {
+                resolveClearOasis(V, region);
+            }
+            break;
         default:
             throw new Error(`Unknown mission type: "${ mission.type }"`);
     }
@@ -30,6 +35,36 @@ export function resolveMission(V: VillageState, region: RegionType) {
 }
 
 
+function resolveClearOasis(V: VillageState, region: OasisType) {
+    const mission = region.state.mission;
+    if (!mission) {
+        return;
+    }
+
+    const ratio = mission.unitCount / region.strength;
+    const lostRatio = 1 / (ratio * ratio);
+    const lostUnits = Math.min(
+        Math.round(mission.unitCount * lostRatio),
+        mission.unitCount
+    );
+
+    mission.unitCount -= lostUnits;
+    V.units.soldier -= lostUnits;
+
+    if (ratio >= 1) {
+        region.state.cleared = true;
+    }
+
+    const unit = getUnitSource('soldier');
+    const maxResources = region.distance * region.distance * 100;
+
+    V.resources[region.resource] += Math.min(
+        mission.unitCount * unit.behavior.caryingCapacity,
+        maxResources
+    );
+}
+
+
 function resolvePillageOasis(V: VillageState, region: OasisType) {
     const mission = region.state.mission;
     if (!mission) {
diff --git a/src/moves/clear.ts b/src/moves/clear.ts
new file mode 100644
index 0000000..d8dc07b
--- /dev/null
+++ b/src/moves/clear.ts
@@ -0,0 +1,28 @@
+import { WORLDMAP_TYPES } from "../types";
+import { assert, getRemainingUnitCount } from "../utils";
+import type { VillageState } from "../village";
+
+
+export default function clear(
+    V: VillageState, regionIndex: number, soldiersCount: number
+) {
+    if (soldiersCount > getRemainingUnitCount(V, 'soldier')) {
+        return false;
+    }
+
+    const region = V.worldmap[regionIndex];
+    assert(region.type === WORLDMAP_TYPES.OASIS);
+
+    if (region.state.mission) {
+        return false;
+    }
+
+    region.state.mission = {
+        type: 'clear',
+        unitType: 'soldier',
+        unitCount: soldiersCount,
+        remainingTime: region.distance * 10 * 1000,
+    };
+
+    return true;
+}
diff --git a/src/moves/index.ts b/src/moves/index.ts
index 10fa278..f860094 100644
--- a/src/moves/index.ts
+++ b/src/moves/index.ts
@@ -2,6 +2,7 @@ import { produce } from 'immer';
 
 import village, { type VillageState } from '../village';
 import build from './build';
+import clear from './clear';
 import pillage from './pillage';
 import recruitUnits from './recruitUnits';
 import startQuest from './startQuest';
@@ -33,6 +34,7 @@ export function makeMove(move: (...args: any[]) => boolean) {
 
 export default {
     build: makeMove(build),
+    clear: makeMove(clear),
     upgradeBuilding: makeMove(upgradeBuilding),
     pillage: makeMove(pillage),
     recruitUnits: makeMove(recruitUnits),
diff --git a/src/moves/pillage.ts b/src/moves/pillage.ts
index 47731b1..aea0029 100644
--- a/src/moves/pillage.ts
+++ b/src/moves/pillage.ts
@@ -3,7 +3,9 @@ import { assert, getRemainingUnitCount } from "../utils";
 import type { VillageState } from "../village";
 
 
-export default function pillage(V: VillageState, regionIndex: number, soldiersCount: number, repeat: boolean) {
+export default function pillage(
+    V: VillageState, regionIndex: number, soldiersCount: number, repeat: boolean
+) {
     if (soldiersCount > getRemainingUnitCount(V, 'soldier')) {
         return false;
     }
@@ -20,7 +22,7 @@ export default function pillage(V: VillageState, regionIndex: number, soldiersCo
         type: 'pillage',
         unitType: 'soldier',
         unitCount: soldiersCount,
-        remainingTime: 1 * 10 * 1000,
+        remainingTime: region.distance * 10 * 1000,
         repeat,
     };
 
diff --git a/src/types.ts b/src/types.ts
index ab96169..8c79dff 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -80,11 +80,11 @@ export interface UnitType {
 
 
 export interface MissionType {
-    type: string;
+    type: 'pillage' | 'clear';
     unitType: string;
     unitCount: number;
     remainingTime: number;
-    repeat: boolean;
+    repeat?: boolean;
 }
 
 
@@ -110,7 +110,9 @@ export interface EmptyRegionType extends BaseRegionType {
 export interface OasisType extends BaseRegionType {
     type: WORLDMAP_TYPES.OASIS;
     resource: keyof CostType;
+    strength: number;
     state: {
+        cleared: boolean;
         mission?: MissionType;
     };
 }
diff --git a/src/utils.ts b/src/utils.ts
index 495020e..36cb3bb 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -213,6 +213,6 @@ export function distanceBetweenCells(a: Point, b: Point) {
 export function indexToPoint(index: number): Point {
     return {
         x: index % WORLD_MAP_WIDTH,
-        y: index / WORLD_MAP_WIDTH,
+        y: Math.floor(index / WORLD_MAP_WIDTH),
     };
 }
diff --git a/src/village.ts b/src/village.ts
index dbe58be..eae3aaa 100644
--- a/src/village.ts
+++ b/src/village.ts
@@ -82,10 +82,9 @@ function getInitialWorldmap(): RegionType[] {
     }
     board[centerIndex].type = WORLDMAP_TYPES.BOURGADE;
 
-    const adj = shuffle(getAdjacentWorldmapCells(centerIndex));
     worldmap.forEach(region => {
         const candidates = board.filter(c =>
-                c.type !== WORLDMAP_TYPES.EMPTY
+                c.type === WORLDMAP_TYPES.EMPTY
                 && c.distance >= region.distance[0]
                 && c.distance < region.distance[1]
         );
@@ -95,7 +94,10 @@ function getInitialWorldmap(): RegionType[] {
             id: cell.id,
             resource: region.resource as keyof CostType,
             distance: cell.distance,
-            state: {},
+            strength: Math.round(cell.distance * cell.distance * 50),
+            state: {
+                cleared: false,
+            },
         };
     });