diff --git a/src/chaos.c b/src/chaos.c
index 58cd7af73..abd74b5d9 100644
--- a/src/chaos.c
+++ b/src/chaos.c
@@ -53,6 +53,19 @@ attrib_type at_chaoscount = {
     ATF_UNIQUE
 };
 
+void set_chaoscount(struct region *r, int deaths)
+{
+    if (deaths==0) {
+        a_removeall(&r->attribs, &at_chaoscount);
+    } else {
+        attrib *a = a_find(r->attribs, &at_chaoscount);
+        if (!a) {
+            a = a_add(&r->attribs, a_new(&at_chaoscount));
+        }
+        a->data.i = deaths;
+    }
+}
+
 int get_chaoscount(const region * r)
 {
     attrib *a = a_find(r->attribs, &at_chaoscount);
diff --git a/src/chaos.h b/src/chaos.h
index 6e62a0d17..0c2667083 100644
--- a/src/chaos.h
+++ b/src/chaos.h
@@ -29,6 +29,7 @@ extern "C" {
     void chaos_register(void);
     void chaos_update(void);
 
+    void set_chaoscount(struct region *r, int deaths);
     int get_chaoscount(const struct region * r);
     void add_chaoscount(struct region * r, int deaths);
 
diff --git a/src/gmtool.c b/src/gmtool.c
index d9afd738e..24c1735e8 100644
--- a/src/gmtool.c
+++ b/src/gmtool.c
@@ -15,6 +15,7 @@
 
 #include "gmtool.h"
 #include "gmtool_structs.h"
+#include "chaos.h"
 #include "console.h"
 #include "listbox.h"
 #include "wormhole.h"
@@ -45,6 +46,7 @@
 #include <attributes/attributes.h>
 #include <triggers/triggers.h>
 
+#include <util/attrib.h>
 #include <util/log.h>
 #include <util/unicode.h>
 #include <util/lists.h>
@@ -515,6 +517,46 @@ static void statusline(WINDOW * win, const char *str)
     wnoutrefresh(win);
 }
 
+static void reset_region(region *r) {
+    set_chaoscount(r, 0);
+    r->flags = 0;
+    a_removeall(&r->attribs, NULL);
+    while (r->units) {
+        remove_unit(&r->units, r->units);
+    }
+    while (r->ships) {
+        remove_ship(&r->ships, r->ships);
+    }
+    while (r->buildings) {
+        remove_building(&r->buildings, r->buildings);
+    }
+}
+
+static void reset_cursor(state *st) {
+    int nx = st->cursor.x;
+    int ny = st->cursor.y;
+    region *r;
+    pnormalize(&nx, &ny, st->cursor.pl);
+    if ((r = findregion(nx, ny)) != NULL) {
+        reset_region(r);
+    }
+}
+
+static void reset_rect(state *st) {
+    int x, y, bs = 3;
+    for (x=0;x!=bs;++x) {
+        for (y = 0; y != bs; ++y) {
+            region *r;
+            int nx = st->cursor.x + x;
+            int ny = st->cursor.y + y;
+            pnormalize(&nx, &ny, st->cursor.pl);
+            if ((r = findregion(nx, ny)) != NULL) {
+                reset_region(r);
+            }
+        }
+    }
+}
+
 static void terraform_at(coordinate * c, const terrain_type * terrain)
 {
     if (terrain != NULL) {
@@ -934,6 +976,12 @@ static void handlekey(state * st, int c)
         st->wnd_status->update |= 1;
         st->wnd_map->update |= 1;
         break;
+    case 'c': /* clear/reset */
+        reset_cursor(st);
+        break;
+    case 'C': /* clear/reset */
+        reset_rect(st);
+        break;
     case 0x09:                 /* tab = next selected */
         if (regions != NULL) {
             map_region *mr = cursor_region(&st->display, cursor);