diff --git a/cmd/rove/main.go b/cmd/rove/main.go
index e00fd9f..17d8dd4 100644
--- a/cmd/rove/main.go
+++ b/cmd/rove/main.go
@@ -214,7 +214,7 @@ func InnerMain(command string, args ...string) error {
 				i++
 				if len(args) == i {
 					return fmt.Errorf("move command must be passed bearing")
-				} else if _, err := maths.FromString(args[i]); err != nil {
+				} else if _, err := maths.BearingFromString(args[i]); err != nil {
 					return err
 				}
 				commands = append(commands,
diff --git a/pkg/maths/bearing.go b/pkg/maths/bearing.go
index 002b06a..e72148b 100644
--- a/pkg/maths/bearing.go
+++ b/pkg/maths/bearing.go
@@ -55,8 +55,8 @@ func (d Bearing) ShortString() string {
 	return bearingStrings[d].Short
 }
 
-// FromString gets the Direction from a string
-func FromString(s string) (Bearing, error) {
+// BearingFromString gets the Direction from a string
+func BearingFromString(s string) (Bearing, error) {
 	for i, d := range bearingStrings {
 		if strings.EqualFold(d.Long, s) || strings.EqualFold(d.Short, s) {
 			return Bearing(i), nil
@@ -80,3 +80,18 @@ var bearingVectors = []Vector{
 func (d Bearing) Vector() Vector {
 	return bearingVectors[d]
 }
+
+// IsCardinal returns if this is a cardinal (NESW)
+func (d Bearing) IsCardinal() bool {
+	switch d {
+	case North:
+		fallthrough
+	case East:
+		fallthrough
+	case South:
+		fallthrough
+	case West:
+		return true
+	}
+	return false
+}
diff --git a/pkg/maths/bearing_test.go b/pkg/maths/bearing_test.go
index bb97043..e0de345 100644
--- a/pkg/maths/bearing_test.go
+++ b/pkg/maths/bearing_test.go
@@ -13,19 +13,19 @@ func TestDirection(t *testing.T) {
 	assert.Equal(t, "N", dir.ShortString())
 	assert.Equal(t, Vector{X: 0, Y: 1}, dir.Vector())
 
-	dir, err := FromString("N")
+	dir, err := BearingFromString("N")
 	assert.NoError(t, err)
 	assert.Equal(t, North, dir)
 
-	dir, err = FromString("n")
+	dir, err = BearingFromString("n")
 	assert.NoError(t, err)
 	assert.Equal(t, North, dir)
 
-	dir, err = FromString("north")
+	dir, err = BearingFromString("north")
 	assert.NoError(t, err)
 	assert.Equal(t, North, dir)
 
-	dir, err = FromString("NorthWest")
+	dir, err = BearingFromString("NorthWest")
 	assert.NoError(t, err)
 	assert.Equal(t, NorthWest, dir)
 }
diff --git a/pkg/rove/world.go b/pkg/rove/world.go
index b3b15a0..4693555 100644
--- a/pkg/rove/world.go
+++ b/pkg/rove/world.go
@@ -426,8 +426,10 @@ func (w *World) Enqueue(rover string, commands ...Command) error {
 	for _, c := range commands {
 		switch c.Command {
 		case roveapi.CommandType_move:
-			if _, err := maths.FromString(c.Bearing); err != nil {
+			if b, err := maths.BearingFromString(c.Bearing); err != nil {
 				return fmt.Errorf("unknown bearing: %s", c.Bearing)
+			} else if !b.IsCardinal() {
+				return fmt.Errorf("bearing must be cardinal")
 			}
 		case roveapi.CommandType_broadcast:
 			if len(c.Message) > 3 {
@@ -505,7 +507,7 @@ func (w *World) ExecuteCommand(c *Command, rover string) (err error) {
 
 	switch c.Command {
 	case roveapi.CommandType_move:
-		if dir, err := maths.FromString(c.Bearing); err != nil {
+		if dir, err := maths.BearingFromString(c.Bearing); err != nil {
 			return err
 		} else if _, err := w.MoveRover(rover, dir); err != nil {
 			return err