diff --git a/GameEngine/HeroBattleBonus.php b/GameEngine/HeroBattleBonus.php
index e1f18aa6..f1365d1b 100644
--- a/GameEngine/HeroBattleBonus.php
+++ b/GameEngine/HeroBattleBonus.php
@@ -469,19 +469,23 @@ class HeroBattleBonus
         $used = array_sum($captured);
         $heroItems->removeItem((int) $uid, (int) $cageRow['id'], $used);
 
-        // Station the animals at home: reuse the self-enforcement row if one
-        // exists (vref = from = home), otherwise create it.
+        // Station the animals at home as a NATURE reinforcement: `from` = 0 is
+        // the engine's existing convention for non-player enforcements (the
+        // "taskmaster" rows) - 16.tpl renders those with tribe 4 columns
+        // (u31-u40, the animal icons) and disables the normal Send back flow,
+        // which would otherwise crash on speed lookup for nature units.
+        // Reuse the row if one exists, otherwise create it.
         $homeWref = (int) $homeWref;
         $res = mysqli_query(
             $database->dblink,
             "SELECT id FROM " . TB_PREFIX . "enforcement
-              WHERE vref = $homeWref AND `from` = $homeWref LIMIT 1"
+              WHERE vref = $homeWref AND `from` = 0 LIMIT 1"
         );
         $rowE = $res ? mysqli_fetch_assoc($res) : null;
         if (!$rowE) {
             mysqli_query(
                 $database->dblink,
-                "INSERT INTO " . TB_PREFIX . "enforcement (vref, `from`) VALUES ($homeWref, $homeWref)"
+                "INSERT INTO " . TB_PREFIX . "enforcement (vref, `from`) VALUES ($homeWref, 0)"
             );
             $enfId = (int) mysqli_insert_id($database->dblink);
         } else {
diff --git a/GameEngine/Lang/en.php b/GameEngine/Lang/en.php
index 71ec7470..a942c88e 100755
--- a/GameEngine/Lang/en.php
+++ b/GameEngine/Lang/en.php
@@ -2821,3 +2821,7 @@ tz_def('HB_TXT_CAGE',       'Captures 1 oasis animal per cage');
 tz_def('HB_TXT_NEEDS_HORSE','requires an equipped horse');
 tz_def('HB_TXT_ONLY',       'only for a');
 tz_def('HB_TXT_HERO',       'hero');
+
+/* T4 hero port - captured animals release action */
+tz_def('HERO_RELEASE_ANIMALS', 'Release');
+tz_def('HERO_RELEASE_CONFIRM', 'Release these animals? They will be gone for good.');
diff --git a/GameEngine/Units.php b/GameEngine/Units.php
index 1ef20ea0..46e84a9b 100755
--- a/GameEngine/Units.php
+++ b/GameEngine/Units.php
@@ -692,6 +692,33 @@ class Units {
      * @param int the ID of the prisoners you want to release
      */
     
+    /**
+     * T4 hero port: destroy a NATURE enforcement row (captured oasis animals,
+     * `from` = 0) stationed in the CURRENT village. Mirrors deletePrisoners'
+     * ownership model: the row must belong to the village the player is
+     * viewing, which the session already validated as theirs. Nature rows
+     * never travel back (no owner village to walk to) - releasing kills them.
+     */
+    public function releaseNatureEnforcement($id){
+        global $village, $database;
+
+        $id = (int) $id;
+        if ($id <= 0) {
+            return false;
+        }
+
+        $stmt = $database->dblink->prepare(
+            "DELETE FROM " . TB_PREFIX . "enforcement
+              WHERE id = ? AND `from` = 0 AND vref = ? LIMIT 1"
+        );
+        $wid = (int) $village->wid;
+        $stmt->bind_param('ii', $id, $wid);
+        $stmt->execute();
+        $ok = $stmt->affected_rows > 0;
+        $stmt->close();
+        return $ok;
+    }
+
     public function deletePrisoners($id){
         global $village, $database, $session, $building, $bid19, $u99;
         
@@ -796,6 +823,16 @@ class Units {
             $speeds[]  = $GLOBALS['u'.$heroUnit]['speed'];
         }
 
+        // Defensive: the tribe-offset loop above only inspects the owner's
+        // own 10 unit columns, so an army made purely of foreign/nature units
+        // (e.g. captured oasis animals) yields no speeds and min() would
+        // fatal (the "Send back" crash). Unreachable through normal flows
+        // now that nature rows disable Send back, but never crash movement
+        // creation - fall back to the slowest common speed.
+        if (empty($speeds)) {
+            $speeds[] = 3;
+        }
+
         $walkTime = $generator->procDistanceTime($fromCor, $toCor, min($speeds), $mode, $from);
 
         // T4 hero port (Phase 5): boots (>20 tiles), pennant (own villages)
diff --git a/Templates/Build/16.tpl b/Templates/Build/16.tpl
index a421fb48..5493414d 100644
--- a/Templates/Build/16.tpl
+++ b/Templates/Build/16.tpl
@@ -93,7 +93,7 @@ $hasRally = $village->resarray['f39'] > 0;
         </tbody>
         <tbody class="infos"><tr><th><?= UPKEEP ?></th><td colspan="<?= $colspan ?>">
             <div class="sup"><?= $technology->getUpkeep($e,$tribe) ?><img class="r4" src="img/x.gif"> <?= PER_HR ?></div>
-            <div class="sback"><?php if(!$isTaskmaster): ?><a href="a2b.php?w=<?= $e['id'] ?>"><?= SEND_BACK ?></a><?php else: ?><span class="none"><b><?= SEND_BACK ?></b></span><?php endif; ?></div>
+            <div class="sback"><?php if(!$isTaskmaster): ?><a href="a2b.php?w=<?= $e['id'] ?>"><?= SEND_BACK ?></a><?php elseif (defined('NEW_FUNCTIONS_HERO_T4') && NEW_FUNCTIONS_HERO_T4): ?><a href="a2b.php?releaseanimals=<?= $e['id'] ?>" onclick="return confirm('<?= defined('HERO_RELEASE_CONFIRM') ? HERO_RELEASE_CONFIRM : 'Release these animals? They will be gone for good.' ?>');"><?= defined('HERO_RELEASE_ANIMALS') ? HERO_RELEASE_ANIMALS : 'Release' ?></a><?php else: ?><span class="none"><b><?= SEND_BACK ?></b></span><?php endif; ?></div>
         </td></tr></tbody>
     </table>
     <?php endforeach; ?>
diff --git a/a2b.php b/a2b.php
index 65ae8199..6ef535a9 100644
--- a/a2b.php
+++ b/a2b.php
@@ -60,6 +60,11 @@ if(isset($_GET['r'])) $r = preg_replace("/[^a-zA-Z0-9_-]/", "", $_GET['r']);
 if(isset($_GET['delprisoners'])){
 	$delprisoners = preg_replace("/[^a-zA-Z0-9_-]/", "", $_GET['delprisoners']);
 }
+// T4 hero port: release (destroy) captured oasis animals from a nature
+// enforcement row (from = 0). Same sanitization as delprisoners.
+if(isset($_GET['releaseanimals'])){
+	$releaseanimals = preg_replace("/[^0-9]/", "", $_GET['releaseanimals']);
+}
 if(isset($_GET['o'])){
 	$o = preg_replace("/[^a-zA-Z0-9_-]/", "", $_GET['o']);
 	$oid = preg_replace("/[^a-zA-Z0-9_-]/", "", $_GET['z']);
@@ -156,6 +161,12 @@ if(!empty($id)){
 		include("Templates/a2b/search.tpl");
 	}
 }else if(isset($delprisoners) && !empty($delprisoners)) $units->deletePrisoners($delprisoners);
+else if(isset($releaseanimals) && !empty($releaseanimals)){
+	// T4 hero port: destroy captured animals, then back to the rally point.
+	$units->releaseNatureEnforcement($releaseanimals);
+	header("Location: build.php?id=39");
+	exit;
+}
 else{
 	if(isset($process['0'])){
 		$coor = $database->getCoor($process['0']);