diff --git a/core/src/com/unciv/logic/automation/unit/UnitAutomation.kt b/core/src/com/unciv/logic/automation/unit/UnitAutomation.kt
index 3ebaf4cb2e..362bc1e211 100644
--- a/core/src/com/unciv/logic/automation/unit/UnitAutomation.kt
+++ b/core/src/com/unciv/logic/automation/unit/UnitAutomation.kt
@@ -142,6 +142,7 @@ object UnitAutomation {
         val upgradeActions = UnitActionsUpgrade.getUpgradeActions(unit)
 
         upgradeActions.firstOrNull{ (it as UpgradeUnitAction).unitToUpgradeTo == upgradedUnit }?.action?.invoke() ?: return false
+        //todo Incorrect - an _unsuccessful_ upgrade might have _resurrected_ the original in which case it's a new clone, and unit.isDestroyed is still true
         return unit.isDestroyed // a successful upgrade action will destroy this unit
     }
 
diff --git a/core/src/com/unciv/logic/map/mapunit/MapUnit.kt b/core/src/com/unciv/logic/map/mapunit/MapUnit.kt
index c07783aed8..9f7005b619 100644
--- a/core/src/com/unciv/logic/map/mapunit/MapUnit.kt
+++ b/core/src/com/unciv/logic/map/mapunit/MapUnit.kt
@@ -377,14 +377,15 @@ class MapUnit : IsPartOfGameInfoSerialization {
     }
 
 
-    fun canFortify(): Boolean {
-        if (baseUnit.isWaterUnit()) return false
-        if (isCivilian()) return false
-        if (baseUnit.movesLikeAirUnits()) return false
-        if (isEmbarked()) return false
-        if (hasUnique(UniqueType.NoDefensiveTerrainBonus)) return false
-        if (isFortified()) return false
-        return true
+    fun canFortify(ignoreAlreadyFortified: Boolean = false) = when {
+        baseUnit.isWaterUnit() -> false
+        isCivilian() -> false
+        baseUnit.movesLikeAirUnits() -> false
+        isEmbarked() -> false
+        hasUnique(UniqueType.NoDefensiveTerrainBonus) -> false
+        ignoreAlreadyFortified -> true
+        isFortified() -> false
+        else -> true
     }
 
     private fun adjacentHealingBonus(): Int {
diff --git a/core/src/com/unciv/logic/map/mapunit/UnitUpgradeManager.kt b/core/src/com/unciv/logic/map/mapunit/UnitUpgradeManager.kt
index 3af0a71ec0..08432b754a 100644
--- a/core/src/com/unciv/logic/map/mapunit/UnitUpgradeManager.kt
+++ b/core/src/com/unciv/logic/map/mapunit/UnitUpgradeManager.kt
@@ -1,11 +1,11 @@
 package com.unciv.logic.map.mapunit
 
-import com.unciv.logic.UncivShowableException
 import com.unciv.models.ruleset.RejectionReasonType
 import com.unciv.models.ruleset.unique.StateForConditionals
 import com.unciv.models.ruleset.unique.UniqueType
 import com.unciv.models.ruleset.unit.BaseUnit
 import com.unciv.ui.components.extensions.toPercent
+import com.unciv.ui.screens.worldscreen.unit.actions.UnitActionsUpgrade
 import kotlin.math.pow
 
 class UnitUpgradeManager(val unit:MapUnit) {
@@ -26,7 +26,7 @@ class UnitUpgradeManager(val unit:MapUnit) {
 
         val rejectionReasons = unitToUpgradeTo.getRejectionReasons(unit.civ, additionalResources = unit.getResourceRequirementsPerTurn())
 
-        var relevantRejectionReasons = rejectionReasons.filterNot { 
+        var relevantRejectionReasons = rejectionReasons.filterNot {
             it.isConstructionRejection() || it.type == RejectionReasonType.Obsoleted
         }
         if (ignoreRequirements)
@@ -68,9 +68,42 @@ class UnitUpgradeManager(val unit:MapUnit) {
         cost = (cost * civModifier).pow(constants.exponent)
         cost *= unit.civ.gameInfo.speed.modifier
         goldCostOfUpgrade += (cost / constants.roundTo).toInt() * constants.roundTo
-        
+
         return goldCostOfUpgrade
     }
 
+    /** _Perform_ an upgrade, assuming validity checks were already passed.
+     *
+     *  Continuing to use a reference to this manager or its unit after this call is invalid!
+     *
+     *  Please use [UnitActionsUpgrade.getUpgradeActions] instead if at all possible.
+     *
+     *  Note - the upgraded unit is a new instance, and it's possible this method will need to place it on a different tile.
+     *  It is also possible the placement fails and the original is resurrected - in which case it is a **new instance** as well.
+     *  It might be desirable to return `newUnit` (or `resurrectedUnit`) if needed -
+     *  but then the lambda in UnitActionsUpgrade will complain and need to be forced back to Unit type.
+     */
+    fun performUpgrade(upgradedUnit: BaseUnit, isFree: Boolean, goldCostOfUpgrade: Int? = null) {
+        unit.destroy(destroyTransportedUnit = false)
+        val civ = unit.civ
+        val position = unit.currentTile.position
+        val newUnit = civ.units.placeUnitNearTile(position, upgradedUnit)
 
+        /** We were UNABLE to place the new unit, which means that the unit failed to upgrade!
+         * The only known cause of this currently is "land units upgrading to water units" which fail to be placed.
+         */
+        if (newUnit == null) {
+            val resurrectedUnit = civ.units.placeUnitNearTile(position, unit.baseUnit)!!
+            unit.copyStatisticsTo(resurrectedUnit)
+            return
+        }
+
+        // Managed to upgrade
+        if (!isFree) civ.addGold(-(goldCostOfUpgrade ?: getCostOfUpgrade(upgradedUnit)))
+        unit.copyStatisticsTo(newUnit)
+        newUnit.currentMovement = 0f
+        // wake up if lost ability to fortify
+        if (newUnit.isFortified() && !newUnit.canFortify(ignoreAlreadyFortified = true))
+            newUnit.action = null
+    }
 }
diff --git a/core/src/com/unciv/ui/screens/worldscreen/unit/actions/UnitActionsUpgrade.kt b/core/src/com/unciv/ui/screens/worldscreen/unit/actions/UnitActionsUpgrade.kt
index a96f6caa9d..cd8ddd62ad 100644
--- a/core/src/com/unciv/ui/screens/worldscreen/unit/actions/UnitActionsUpgrade.kt
+++ b/core/src/com/unciv/ui/screens/worldscreen/unit/actions/UnitActionsUpgrade.kt
@@ -60,20 +60,7 @@ object UnitActionsUpgrade {
                 goldCostOfUpgrade = goldCostOfUpgrade,
                 newResourceRequirements = resourceRequirementsDelta,
                 action = {
-                    unit.destroy(destroyTransportedUnit = false)
-                    val newUnit = civInfo.units.placeUnitNearTile(unitTile.position, upgradedUnit)
-
-                    /** We were UNABLE to place the new unit, which means that the unit failed to upgrade!
-                     * The only known cause of this currently is "land units upgrading to water units" which fail to be placed.
-                     */
-                    if (newUnit == null) {
-                        val resurrectedUnit = civInfo.units.placeUnitNearTile(unitTile.position, unit.baseUnit)!!
-                        unit.copyStatisticsTo(resurrectedUnit)
-                    } else { // Managed to upgrade
-                        if (!isFree) civInfo.addGold(-goldCostOfUpgrade)
-                        unit.copyStatisticsTo(newUnit)
-                        newUnit.currentMovement = 0f
-                    }
+                    unit.upgrade.performUpgrade(upgradedUnit, isFree, goldCostOfUpgrade)
                 }.takeIf {
                     isFree || (
                         unit.civ.gold >= goldCostOfUpgrade