As for the g4/b4 moves, he tried them in only four games. Was there any particular characteristic of the start positions that led him to choose these moves? I'll look at that question in another post.
Here is a list of the four games:-
- SP452 RBBNNKQR: 2009.06.25, Smallville - Dreev
- SP931 BRKRNQNB: 2009.07.27, Smallville - OfficeMan
- SP751 RKNNQRBB: 2010.06.02, Smallville - TheDuns
- SP121 NQRBBNKR: 2010.06.27, Smallville - Shadeath
The following diagram shows the position after Nakamura's first move in each game. The first characteristic of the four positions is that -- even before the initial Pawn move -- White has already decided to castle to the wing opposite the Pawn move. The second position, SP931 BRKRNQNB, is the least certain. Since the d-Rook interferes with O-O-O and must move out of the way, castles O-O is a good alternative.
The second characteristic of the four positions is that the Pawn move aids development. In the first three positions -- SP452, SP931, and SP751 -- the initial move opens a diagonal for a Bishop. The same objective could be accomplished by advancing the Pawn a single rank. By advancing two ranks, White prepares the advance of the the adjacent c-/f-Pawn with a gain of space on that wing.
The fourth position -- SP121 -- does nothing directly for a Bishop, but it does prepare the development of the Queen on the long diagonal. It also prepares a protected base for the Knight on b3, and after a subsequent c2-c4, prepares to bring out the light-squared Bishop on the a4-d1 diagonal.
In all of these positions, it's easy to find another, more traditional first move -- 1.c4, 1.d4, 1.e4, or 1.f4 -- that respects the principle of center control, but Nakamura's choice is not at all bad. Considering that all of the games were played at bullet speed (three minutes per side plus increment of a second or two per move), the American GM presented his opponents with unfamiliar problems to solve in a short time. He won all four games.