diff --git a/include/sect.h b/include/sect.h
index ec577043..d2598c5c 100644
--- a/include/sect.h
+++ b/include/sect.h
@@ -164,7 +164,7 @@ extern int sctoff(coord x, coord y);
 
 extern struct dchrstr dchr[SCT_MAXDEF + 1];
 extern struct dchrstr bigcity_dchr;
-#define IS_BIG_CITY(sect) (dchr[(sect)].d_pkg == UPKG)
+#define IS_BIG_CITY(type) (dchr[(type)].d_pkg == UPKG)
 
 /* Minimal efficiency of sectors that can be knocked down (bridges) */
 #define SCT_MINEFF 20
@@ -178,10 +178,9 @@ extern struct dchrstr bigcity_dchr;
 #define MIN_MOBCOST  0.001	/* lowest cost a sector can have to move into */
 #define FORTEFF 5		/* forts must be 5% efficient to fire. */
 
-#define MOB_NONE    0
-#define MOB_MOVE    1
-#define MOB_MARCH   2
-#define MOB_RAIL    3
+#define MOB_MOVE    0
+#define MOB_MARCH   1
+#define MOB_RAIL    2
 
 #define INT_ROAD    0
 #define INT_RAIL    1
diff --git a/src/lib/common/move.c b/src/lib/common/move.c
index 093b5cb4..931a909d 100644
--- a/src/lib/common/move.c
+++ b/src/lib/common/move.c
@@ -41,7 +41,7 @@
 #include "common.h"
 
 double
-sector_mcost(struct sctstr *sp, int do_bonus)
+sector_mcost(struct sctstr *sp, int mobtype)
 {
     double d;
 
@@ -49,16 +49,15 @@ sector_mcost(struct sctstr *sp, int do_bonus)
     if (d <= 0)
 	return -1.0;
 
-    if (do_bonus == MOB_MOVE || do_bonus == MOB_MARCH) {
+    if (mobtype == MOB_MOVE || mobtype == MOB_MARCH) {
 	d = d / (1.0 + sp->sct_road / 122.0);
-    } else if (do_bonus == MOB_RAIL) {
+    } else if (mobtype == MOB_RAIL) {
 	if (sp->sct_rail <= 0)
 	    return -1.0;
 	d = d / (1.0 + sp->sct_rail / 100.0);
-    } else {
-	if (d < 2.0)
-	    d = 2.0;
-    }
+    } else
+	CANT_REACH();
+
     if (d < 1.0)
 	d = 1.0;
     if (dchr[sp->sct_type].d_mcst < 25)
@@ -66,10 +65,10 @@ sector_mcost(struct sctstr *sp, int do_bonus)
     else
 	d = (d * 10.0 - sp->sct_effic) / 115;
 
-    if (do_bonus == MOB_MOVE)
+    if (mobtype == MOB_MOVE)
 	return MAX(d, MIN_MOBCOST);
     if (sp->sct_own != sp->sct_oldown && sp->sct_mobil <= 0
-	&& do_bonus != MOB_RAIL)
+	&& mobtype != MOB_RAIL)
 	return MAX(d, LND_MINMOBCOST);
     return MAX(d, 0.01);
 }
diff --git a/src/lib/subs/attsub.c b/src/lib/subs/attsub.c
index cffce1e5..effb37e4 100644
--- a/src/lib/subs/attsub.c
+++ b/src/lib/subs/attsub.c
@@ -783,21 +783,51 @@ att_ask_offense(int combat_mode, struct combat *off, struct combat *def,
     return 0;
 }
 
+/*
+ * Return path cost for ATTACKER to enter sector given by DEF.
+ * MOBTYPE is a mobility type accepted by sector_mcost().
+ */
+static double
+att_mobcost(natid attacker, struct combat *def, int mobtype)
+{
+    struct sctstr sect;
+    int ok;
+
+    if (CANT_HAPPEN(def->type != EF_SECTOR))
+	return -1.0;
+    ok = getsect(def->x, def->y, &sect);
+    if (CANT_HAPPEN(!ok))
+	return -1.0;
+
+    /*
+     * We want the cost to move/march into the sector.  If we just
+     * called sector_mcost(), we'd get the defender's cost.  The
+     * attacker's cost is higher unless he's the old-owner.  Note: if
+     * there are no civilians, a victorious attacker will become the
+     * old-owner.  But he isn't now.
+     */
+    sect.sct_own = attacker;
+    sect.sct_mobil = 0;
+    return sector_mcost(&sect, mobtype);
+}
+
 /* How many mil is off allowed to attack with when it attacks def? */
 
 static int
 get_mob_support(int combat_mode, struct combat *off, struct combat *def)
 {
     int mob_support;
+    double mobcost;
 
     switch (combat_mode) {
     case A_ATTACK:
-	mob_support = off->mob / sector_mcost(getsectp(def->x, def->y),
-					      MOB_MOVE);
-	if (mob_support < 0)
-	    mob_support = 0;
+	mobcost = att_mobcost(off->own, def, MOB_MOVE);
+	if (mobcost < 0 || off->mob <= 0)
+	    return 0;
+	mob_support = off->mob / mobcost;
 	if (mob_support < off->troops)
-	    pr("Sector %s has %d mobility which can only support %d mil,\n", xyas(off->x, off->y, player->cnum), off->mob, mob_support);
+	    pr("Sector %s has %d mobility which can only support %d mil,\n",
+	       xyas(off->x, off->y, player->cnum), off->mob, mob_support);
 	else
 	    mob_support = off->troops;
 	return mob_support;
@@ -850,10 +880,9 @@ calc_mobcost(int combat_mode, struct combat *off, struct combat *def,
 	return;
     switch (combat_mode) {
     case A_ATTACK:
-	off->mobcost +=
-	    MAX(1,
-		(int)(attacking_mil *
-		      sector_mcost(getsectp(def->x, def->y), MOB_MOVE)));
+	off->mobcost += MAX(1,
+			    (int)(attacking_mil
+				  * att_mobcost(off->own, def, MOB_MOVE)));
 	break;
     case A_LBOARD:
 	off->mobcost += MAX(1, attacking_mil / 5);
@@ -1008,8 +1037,8 @@ ask_olist(int combat_mode, struct combat *off, struct combat *def,
 	}
 	switch (combat_mode) {
 	case A_ATTACK:
-	    mobcost =
-		lnd_mobcost(&land, getsectp(def->x, def->y), MOB_NONE);
+	    mobcost = lnd_pathcost(&land,
+				   att_mobcost(off->own, def, MOB_MARCH));
 	    if (land.lnd_mobil < mobcost) {
 		pr("%s does not have enough mobility (%d needed)\n",
 		   prland(&land), (int)ceil(mobcost));
@@ -1103,10 +1132,6 @@ att_combat_eff(struct combat *com)
     return eff;
 }
 
-/*
- * Estimate the defense strength and give the attacker a chance to abort
- * if the odds are less than 50%
- */
 int
 att_get_offense(int combat_mode, struct combat *off,
 		struct emp_qelem *olist, struct combat *def)
@@ -2441,7 +2466,7 @@ ask_move_in_off(struct combat *off, struct combat *def)
 	return;
     if (off->own != player->cnum)
 	return;
-    d = sector_mcost(getsectp(def->x, def->y), MOB_MOVE);
+    d = att_mobcost(off->own, def, MOB_MOVE);
     if ((mob_support = MIN(off->troops, (int)(off->mob / d))) <= 0)
 	return;
     sprintf(prompt, "How many mil to move in from %s (%d max)? ",
@@ -2503,8 +2528,8 @@ take_move_in_mob(int combat_mode, struct llist *llp, struct combat *off,
 
     switch (combat_mode) {
     case A_ATTACK:
-	mobcost =
-	    lnd_mobcost(&llp->land, getsectp(def->x, def->y), MOB_NONE);
+	mobcost = lnd_pathcost(&llp->land,
+			       att_mobcost(off->own, def, MOB_MARCH));
 	new = llp->land.lnd_mobil - mobcost;
 	if (new < -127)
 	    new = -127;