diff --git a/hwe/sammo/Constraint/ConstraintHelper.php b/hwe/sammo/Constraint/ConstraintHelper.php
index b3842a88..e354eaf6 100644
--- a/hwe/sammo/Constraint/ConstraintHelper.php
+++ b/hwe/sammo/Constraint/ConstraintHelper.php
@@ -3,7 +3,7 @@
 namespace sammo\Constraint;
 
 class ConstraintHelper{
-    
+
     static function AdhocCallback(callable $callback):array{
         return [__FUNCTION__, $callback];
     }
@@ -19,7 +19,7 @@ class ConstraintHelper{
     static function AllowDiplomacyWithTerm(int $allowDipCode, int $allowMinTerm, string $errMsg):array{
         return [__FUNCTION__, [$allowDipCode, $allowMinTerm, $errMsg]];
     }
-    
+
     static function AllowJoinAction():array{
         return [__FUNCTION__];
     }
@@ -67,11 +67,11 @@ class ConstraintHelper{
     static function BeOpeningPart(int $relYear):array{
         return [__FUNCTION__, $relYear];
     }
-    
+
     static function CheckNationNameDuplicate(string $nationName):array{
         return [__FUNCTION__, $nationName];
     }
-    
+
     static function ConstructableCity():array{
         return [__FUNCTION__];
     }
@@ -99,11 +99,11 @@ class ConstraintHelper{
     static function ExistsDestGeneral():array{
         return [__FUNCTION__];
     }
-    
+
     static function ExistsDestNation():array{
         return [__FUNCTION__];
     }
-    
+
     static function FriendlyDestGeneral():array{
         return [__FUNCTION__];
     }
@@ -123,7 +123,7 @@ class ConstraintHelper{
     static function MustBeTroopLeader():array{
         return [__FUNCTION__];
     }
-    
+
     static function NearCity(int $distance):array{
         return [__FUNCTION__, $distance];
     }
@@ -132,6 +132,10 @@ class ConstraintHelper{
         return [__FUNCTION__];
     }
 
+    static function NeutralCity():array{
+        return [__FUNCTION__];
+    }
+
     static function NotBeNeutral():array{
         return [__FUNCTION__];
     }
@@ -175,11 +179,11 @@ class ConstraintHelper{
     static function OccupiedDestCity():array{
         return [__FUNCTION__];
     }
-    
+
     static function RemainCityCapacity($key, string $actionName):array{
         return [__FUNCTION__, [$key, $actionName]];
     }
-    
+
     static function RemainCityTrust(string $actionName):array{
         return [__FUNCTION__, $actionName];
     }
@@ -187,7 +191,7 @@ class ConstraintHelper{
     static function ReqCityCapacity($key, string $keyNick, $reqVal):array{
         return [__FUNCTION__, [$key, $keyNick, $reqVal]];
     }
-    
+
     static function ReqCityTrust(float $minTrust):array{
         return [__FUNCTION__, $minTrust];
     }
@@ -267,7 +271,7 @@ class ConstraintHelper{
     static function SuppliedDestCity():array{
         return [__FUNCTION__];
     }
-    
+
     static function WanderingNation():array{
         return [__FUNCTION__];
     }
diff --git a/hwe/sammo/Constraint/NeutralCity.php b/hwe/sammo/Constraint/NeutralCity.php
new file mode 100644
index 00000000..718e4852
--- /dev/null
+++ b/hwe/sammo/Constraint/NeutralCity.php
@@ -0,0 +1,32 @@
+<?php
+
+namespace sammo\Constraint;
+
+class NeutralCity extends Constraint{
+    const REQ_VALUES = Constraint::REQ_CITY;
+
+    public function checkInputValues(bool $throwExeception=true):bool{
+        if(!parent::checkInputValues($throwExeception) && !$throwExeception){
+            return false;
+        }
+
+        if(!key_exists('nation', $this->city)){
+            if(!$throwExeception){return false; }
+            throw new \InvalidArgumentException("require nation in city");
+        }
+
+        return true;
+    }
+
+    public function test():bool{
+        $this->checkInputValues();
+        $this->tested = true;
+
+        if($this->city['nation'] == 0){
+            return true;
+        }
+
+        $this->reason = "공백지가 아닙니다.";
+        return false;
+    }
+}
\ No newline at end of file