diff --git a/core/src/com/unciv/logic/civilization/diplomacy/CityStateFunctions.kt b/core/src/com/unciv/logic/civilization/diplomacy/CityStateFunctions.kt
index 25fd5b8323..26ec998736 100644
--- a/core/src/com/unciv/logic/civilization/diplomacy/CityStateFunctions.kt
+++ b/core/src/com/unciv/logic/civilization/diplomacy/CityStateFunctions.kt
@@ -316,6 +316,10 @@ class CityStateFunctions(val civInfo: Civilization) {
                     NotificationCategory.Diplomacy, civInfo.civName,
                     NotificationIcon.Diplomacy
                 )
+                if (newAllyName != null && oldAllyCiv.knows(newAllyName)){
+                    val diplomacyManager = oldAllyCiv.getDiplomacyManager(newAllyName)!!
+                    diplomacyManager.addModifier(DiplomaticModifiers.StoleOurAlly, -10f)
+                }
                 oldAllyCiv.cache.updateViewableTiles()
                 oldAllyCiv.cache.updateCivResources()
             }
diff --git a/core/src/com/unciv/logic/civilization/diplomacy/DiplomacyManager.kt b/core/src/com/unciv/logic/civilization/diplomacy/DiplomacyManager.kt
index f39d47d884..f0eb6f5c75 100644
--- a/core/src/com/unciv/logic/civilization/diplomacy/DiplomacyManager.kt
+++ b/core/src/com/unciv/logic/civilization/diplomacy/DiplomacyManager.kt
@@ -104,6 +104,7 @@ enum class DiplomaticModifiers(val text: String) {
     BulliedProtectedMinor("You demanded tribute from City-States that were under our protection!"),
     SidedWithProtectedMinor("You sided with a City-State over us"),
     SpiedOnUs("You spied on us!"),
+    StoleOurAlly("You took the alliance we had with a City-State"),
 
     // Positive
     YearsOfPeace("Years of peace have strengthened our relations."),
diff --git a/core/src/com/unciv/logic/civilization/diplomacy/DiplomacyTurnManager.kt b/core/src/com/unciv/logic/civilization/diplomacy/DiplomacyTurnManager.kt
index 98364ba4fa..0133b3efe9 100644
--- a/core/src/com/unciv/logic/civilization/diplomacy/DiplomacyTurnManager.kt
+++ b/core/src/com/unciv/logic/civilization/diplomacy/DiplomacyTurnManager.kt
@@ -292,6 +292,7 @@ object DiplomacyTurnManager {
         revertToZero(DiplomaticModifiers.DenouncedOurEnemies, 1 / 4f)
         revertToZero(DiplomaticModifiers.Denunciation, 1 / 8f) // That's personal, it'll take a long time to fade
         revertToZero(DiplomaticModifiers.SpiedOnUs, 1 / 4f)
+        revertToZero(DiplomaticModifiers.StoleOurAlly, 1 / 2f) // Fair enough, don't like it but not directly against us per se
 
         // Positives
         revertToZero(DiplomaticModifiers.GaveUsUnits, 1 / 4f)