White's last move was Ra2. I was to curious to know the plan behind or any strategical / tactical significance behind that move.
Ra2 moves the rook off the diagonal of the g7 bishop thereby preempting any tactical tricks that might occur later. It is better than Rb1 since then Qa5 would embarrass the bishop on a3.
It also leaves b1 free for the queen later when white wants to exert more pressure down the h1-a8 diagonal of his g2 bishop against b7 and c6. Black has a passed a pawn and white must generate pressure in this area in the medium term if the pawn is not to win the game for black in the long term.
I think white's plan is to play Ra2-Qa1, followed by 0-0 Rb1, and maybe Rab2 in the future if necessary.
The idea, I think is the apply pressure on black's queen side, and preventing the development of black's queen side pieces.
The attack can become deadly if another piece follows the attack after the Rooks double. Example: Bc5 - attacking d4 and a7.
He's clearing the Rook off the
h8 diagonal. White signals that he intends to remove the pawn on
d4 or fears Black will do the same. The point is to remove Black's ability to fabricate a double-attack.
That being said, I'm not sure it was the time to play the move. Castling looks like a better move.