diff --git a/doc/protocol.txt b/doc/protocol.txt
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+Positions:
+
+ 0123456789
+A 
+B
+C
+D
+E
+F
+G
+H
+
+(positions are denoted by row and column, e.g. D4)
+
+Directions:
+
+NW  N  NE
+W   x   E
+SW  S  SE
+
+Rotations:
+
+L, R (or CW, CCW)
+
+Messages:
+
+M[OVE] position direction
+R[OTATE] position rotation
+
+Example:
+
+M F5 NW