repetition_count = 1; history_index = 4
  9    8    7    6    5    4    3    2    1  
+----+----+----+----+----+----+----+----+----+
| Lw | Nw |    | Gw | Kw | Gw | Sw | Nw | Lw | a   
+----+----+----+----+----+----+----+----+----+
|    | Rw | Sw |    |    |    |    | Bw |    | b
+----+----+----+----+----+----+----+----+----+
| Pw | Pw | Pw | Pw | Pw | Pw |    | Pw | Pw | c
+----+----+----+----+----+----+----+----+----+
|    |    |    |    |    |    | Pw |    |    | d
+----+----+----+----+----+----+----+----+----+
|    |    |    |    |    |    |    |    |    | e
+----+----+----+----+----+----+----+----+----+
|    |    |    |    |    |    |    |    |    | f
+----+----+----+----+----+----+----+----+----+
| Pb | Pb | Pb | Pb | Pb | Pb | Pb | Pb | Pb | g
+----+----+----+----+----+----+----+----+----+
|    | Bb | Gb | Sb |    |    |    | Rb |    | h
+----+----+----+----+----+----+----+----+----+
| Lb | Nb |    |    | Kb | Gb | Sb | Nb | Lb | i * 
+----+----+----+----+----+----+----+----+----+