diff --git a/client/CMakeLists.txt b/client/CMakeLists.txt
index e735b6e846..c7a2b4744c 100644
--- a/client/CMakeLists.txt
+++ b/client/CMakeLists.txt
@@ -124,6 +124,7 @@ target_sources(
   utils/colorizer.cpp
   utils/improvement_seller.cpp
   utils/unit_quick_menu.cpp
+  utils/unit_utils.cpp
   views/view_cities.cpp
   views/view_cities_data.cpp
   views/view_economics.cpp
diff --git a/client/citydlg.cpp b/client/citydlg.cpp
index 8e56d80e2a..99a6789b65 100644
--- a/client/citydlg.cpp
+++ b/client/citydlg.cpp
@@ -26,6 +26,7 @@
 // utility
 #include "fc_types.h"
 #include "fcintl.h"
+#include "player.h"
 #include "support.h"
 // common
 #include "citizens.h"
@@ -54,6 +55,7 @@
 #include "unitlist.h"
 #include "utils/improvement_seller.h"
 #include "utils/unit_quick_menu.h"
+#include "utils/unit_utils.h"
 #include "views/view_cities.h" // hIcon
 #include "views/view_map.h"
 #include "views/view_map_common.h"
@@ -102,8 +104,7 @@ void unit_list_widget::set_units(unit_list *units)
   clear();
 
   QSize icon_size;
-  unit_list_iterate(units, punit)
-  {
+  for (const auto *punit : sorted(units)) {
     auto *item = new QListWidgetItem();
     item->setToolTip(unit_description(punit));
     item->setData(Qt::UserRole, punit->id);
@@ -113,7 +114,6 @@ void unit_list_widget::set_units(unit_list *units)
     item->setIcon(QIcon(pixmap));
     addItem(item);
   }
-  unit_list_iterate_end;
 
   setGridSize(icon_size);
   setIconSize(icon_size);
@@ -1763,77 +1763,6 @@ void city_dialog::dbl_click_p(QTableWidgetItem *item)
   city_set_queue(pcity, &queue);
 }
 
-namespace /* anonymous */ {
-/**
- * Finds how deeply the unit is nested in transports.
- */
-int transport_depth(const unit *unit)
-{
-  int depth = 0;
-  for (auto parent = unit->transporter; parent != nullptr;
-       parent = parent->transporter) {
-    depth++;
-  }
-  return depth;
-}
-
-/**
- * Comparison function to sort units as shown in the city dialog.
- */
-int units_sort(const unit *const *plhs, const unit *const *prhs)
-{
-  if (plhs == prhs || *plhs == *prhs) {
-    return 0;
-  }
-
-  auto lhs = *plhs;
-  auto rhs = *prhs;
-
-  // Transports are shown before the units they transport.
-  if (lhs == rhs->transporter) {
-    return false;
-  } else if (lhs->transporter == rhs) {
-    return true;
-  }
-
-  // When one unit is deeper or the two transporters are different, compare
-  // the parents instead.
-  int lhs_depth = transport_depth(lhs);
-  int rhs_depth = transport_depth(rhs);
-  if (lhs_depth > rhs_depth) {
-    return units_sort(&lhs->transporter, &rhs);
-  } else if (lhs_depth < rhs_depth) {
-    return units_sort(&lhs, &rhs->transporter);
-  } else if (lhs->transporter != rhs->transporter) {
-    return units_sort(&lhs->transporter, &rhs->transporter);
-  }
-
-  // Put defensive units on the left
-  if (lhs->utype->defense_strength != rhs->utype->defense_strength) {
-    return rhs->utype->defense_strength - lhs->utype->defense_strength;
-  }
-
-  // Put fortified units on the left, then fortifying units, then sentried
-  // units.
-  for (auto activity :
-       {ACTIVITY_FORTIFIED, ACTIVITY_FORTIFYING, ACTIVITY_SENTRY}) {
-    if (lhs->activity == activity && rhs->activity != activity) {
-      return false;
-    } else if (lhs->activity != activity && rhs->activity == activity) {
-      return true;
-    }
-  }
-
-  // Order by unit type
-  if (lhs->utype != rhs->utype) {
-    return lhs->utype->item_number - rhs->utype->item_number;
-  }
-
-  // Then unit id
-  return lhs->id - rhs->id;
-}
-} // anonymous namespace
-
 /**
    Updates layouts for supported and present units in city
  */
diff --git a/client/text.cpp b/client/text.cpp
index ff275aaa48..907e787624 100644
--- a/client/text.cpp
+++ b/client/text.cpp
@@ -548,7 +548,7 @@ const QString get_nearest_city_text(struct city *pcity, int sq_dist)
    FIXME: This function is not re-entrant because it returns a pointer to
    static data.
  */
-const QString unit_description(struct unit *punit)
+const QString unit_description(const unit *punit)
 {
   int pcity_near_dist;
   struct player *owner = unit_owner(punit);
diff --git a/client/text.h b/client/text.h
index 91202e7c49..e9ee1aa605 100644
--- a/client/text.h
+++ b/client/text.h
@@ -24,7 +24,7 @@ struct player_spaceship;
 const QString get_tile_output_text(const struct tile *ptile);
 const QString popup_info_text(struct tile *ptile);
 const QString get_nearest_city_text(struct city *pcity, int sq_dist);
-const QString unit_description(struct unit *punit);
+const QString unit_description(const unit *punit);
 const QString get_airlift_text(const std::vector<unit *> &units,
                                const struct city *pdest);
 const QString science_dialog_text();
diff --git a/client/unitselect.cpp b/client/unitselect.cpp
index a837340353..d4a2199672 100644
--- a/client/unitselect.cpp
+++ b/client/unitselect.cpp
@@ -26,6 +26,7 @@
 #include "fonts.h"
 #include "page_game.h"
 #include "tileset/tilespec.h"
+#include "utils/unit_utils.h"
 #include "views/view_map.h"
 #include "views/view_map_common.h"
 
@@ -76,7 +77,7 @@ void units_select::create_pixmap()
   QPixmap *tmp_pix;
   QRect crop;
   QPixmap *unit_pixmap;
-  struct unit *punit;
+  const unit *punit;
   float isosize;
 
   delete pix;
@@ -86,7 +87,7 @@ void units_select::create_pixmap()
   }
 
   update_units();
-  if (unit_list.count() > 0) {
+  if (!unit_list.empty()) {
     if (!tileset_is_isometric(tileset)) {
       item_size.setWidth(tileset_unit_width(tileset));
       item_size.setHeight(tileset_unit_width(tileset));
@@ -211,14 +212,12 @@ void units_select::mouseMoveEvent(QMouseEvent *event)
  */
 void units_select::mousePressEvent(QMouseEvent *event)
 {
-  struct unit *punit;
   if (event->button() == Qt::LeftButton && highligh_num != -1) {
     update_units();
-    if (highligh_num >= unit_list.count()) {
+    if (highligh_num >= unit_list.size()) {
       return;
     }
-    punit = unit_list.at(highligh_num);
-    unit_focus_set(punit);
+    unit_focus_set(unit_list.at(highligh_num));
   }
   QMenu::mousePressEvent(event);
 }
@@ -234,7 +233,6 @@ void units_select::paint(QPainter *painter, QPaintEvent *event)
   int *f_size;
   QPen pen;
   QString str, str2, unit_name;
-  struct unit *punit;
   int point_size = info_font.pointSize();
   int pixel_size = info_font.pixelSize();
 
@@ -243,8 +241,8 @@ void units_select::paint(QPainter *painter, QPaintEvent *event)
   } else {
     f_size = &point_size;
   }
-  if (highligh_num != -1 && highligh_num < unit_list.count()) {
-    punit = unit_list.at(highligh_num);
+  if (highligh_num != -1 && highligh_num < unit_list.size()) {
+    auto punit = unit_list.at(highligh_num);
     // TRANS: HP - hit points
     unit_name = unit_name_translation(punit);
     str2 = QString(_("%1 HP:%2/%3"))
@@ -271,7 +269,7 @@ void units_select::paint(QPainter *painter, QPaintEvent *event)
     painter->setPen(pen);
     painter->setFont(info_font);
     painter->drawText(10, h, str);
-    if (highligh_num != -1 && highligh_num < unit_list.count()) {
+    if (highligh_num != -1 && highligh_num < unit_list.size()) {
       painter->drawText(10, height() - 5 - h, unit_name);
       painter->drawText(10, height() - 5, str2);
     }
@@ -332,18 +330,16 @@ void units_select::update_units()
   if (utile != nullptr) {
     punit_list = utile->units;
     if (punit_list != nullptr) {
-      unit_list_iterate(utile->units, punit)
-      {
+      for (auto *punit : sorted(utile->units)) {
         unit_count++;
         if (i > show_line * column_count) {
           unit_list.push_back(punit);
         }
         i++;
       }
-      unit_list_iterate_end;
     }
   }
-  if (unit_list.count() == 0) {
+  if (unit_list.empty()) {
     close();
   }
 }
diff --git a/client/unitselect.h b/client/unitselect.h
index a3411add07..097ae43bf1 100644
--- a/client/unitselect.h
+++ b/client/unitselect.h
@@ -14,6 +14,8 @@
 
 #include <QMenu>
 
+#include <vector>
+
 class QPixmap;
 class QSize;
 class QFont;
@@ -27,10 +29,9 @@ class units_select : public QMenu {
   Q_OBJECT
   Q_DISABLE_COPY(units_select);
   QPixmap *pix;
-  QPixmap *h_pix;          /** pixmap for highlighting */
-  QSize item_size;         /** size of each pixmap of unit */
-  QList<unit *> unit_list; /** storing units only for drawing, for rest units
-                            * iterate utile->units */
+  QPixmap *h_pix;                /** pixmap for highlighting */
+  QSize item_size;               /** size of each pixmap of unit */
+  std::vector<unit *> unit_list; ///< units currently visible
   QFont ufont;
   QFont info_font;
   int column_count, row_count;
diff --git a/client/utils/unit_utils.cpp b/client/utils/unit_utils.cpp
new file mode 100644
index 0000000000..30307cfefd
--- /dev/null
+++ b/client/utils/unit_utils.cpp
@@ -0,0 +1,96 @@
+// SPDX-FileCopyrightText: Louis Moureaux <m_louis30@yahoo.com>
+// SPDX-License-Identifier: GPLv3-or-later
+
+#include "unit_utils.h"
+
+#include "player.h"
+#include "unit.h"
+#include "unitlist.h"
+
+#include <algorithm>
+
+namespace /* anonymous */ {
+/**
+ * Finds how deeply the unit is nested in transports.
+ */
+int transport_depth(const unit *unit)
+{
+  int depth = 0;
+  for (auto parent = unit->transporter; parent != nullptr;
+       parent = parent->transporter) {
+    depth++;
+  }
+  return depth;
+}
+
+/**
+ * Comparison function to sort units. Used in the city dialog and the unit
+ * selector.
+ */
+bool units_sort(const unit *lhs, const unit *rhs)
+{
+  if (lhs == rhs) {
+    return 0;
+  }
+
+  // Transports are shown before the units they transport.
+  if (lhs == rhs->transporter) {
+    return true;
+  } else if (lhs->transporter == rhs) {
+    return false;
+  }
+
+  // When one unit is deeper or the two transporters are different, compare
+  // the parents instead.
+  int lhs_depth = transport_depth(lhs);
+  int rhs_depth = transport_depth(rhs);
+  if (lhs_depth > rhs_depth) {
+    return units_sort(lhs->transporter, rhs);
+  } else if (lhs_depth < rhs_depth) {
+    return units_sort(lhs, rhs->transporter);
+  } else if (lhs->transporter != rhs->transporter) {
+    return units_sort(lhs->transporter, rhs->transporter);
+  }
+
+  // Put defensive units on the left - these are least likely to move, having
+  // them first makes the list more stable
+  const auto lhs_def = lhs->utype->defense_strength * lhs->utype->hp;
+  const auto rhs_def = rhs->utype->defense_strength * rhs->utype->hp;
+  if (lhs_def != rhs_def) {
+    return lhs_def > rhs_def;
+  }
+
+  // More veteran units further left
+  if (lhs->veteran != rhs->veteran) {
+    return lhs->veteran > rhs->veteran;
+  }
+
+  // Reverse order by unit type - in most ruleset this means old units last
+  if (lhs->utype != rhs->utype) {
+    return lhs->utype->item_number > rhs->utype->item_number;
+  }
+
+  // By nationality so units from the same player are grouped together
+  if (player_index(lhs->nationality) != player_index(rhs->nationality)) {
+    return player_index(lhs->nationality) < player_index(rhs->nationality);
+  }
+
+  // Then unit id
+  return lhs->id < rhs->id;
+}
+} // anonymous namespace
+
+/**
+ * Returns a version of \c units sorted in the way the user would like to see
+ * them.
+ */
+std::vector<unit *> sorted(const unit_list *units)
+{
+  std::vector<unit *> vec;
+  unit_list_iterate(units, unit) { vec.push_back(unit); }
+  unit_list_iterate_end;
+
+  std::sort(vec.begin(), vec.end(), units_sort);
+
+  return vec;
+}
diff --git a/client/utils/unit_utils.h b/client/utils/unit_utils.h
new file mode 100644
index 0000000000..4d6175a807
--- /dev/null
+++ b/client/utils/unit_utils.h
@@ -0,0 +1,11 @@
+// SPDX-FileCopyrightText: Louis Moureaux <m_louis30@yahoo.com>
+// SPDX-License-Identifier: GPLv3-or-later
+
+#pragma once
+
+#include <vector>
+
+struct unit;
+struct unit_list;
+
+std::vector<unit *> sorted(const unit_list *units);