Rh-e1 is probably better, but this move is necessary (Nb4 threatening Nxa2, rather do it now than be sorry later).

At last black completes his opening - except for Kb8 which he needs at some point, but look at the position.. White is in control of the centre, the black diagonal, the white diagonal, open files for his rooks.. On the other side, black's pieces standing in their own way, where can the Knight go? Where does the white bishop move to, the black bishop is poorly placed, blocking his own pawn from advancing... Positionally, white has the advantage..

Of course, threatening d5.. chasing the Knight into the corner, where he will be weakest..

Well well.. the Queen still under threat (pawn on e6 can't take), Knight still has no place to go. Bishop on d7 now completely blocked in, Rook on d8 completely blocked in.. Queen completely blocked in.. let's see (d5 Na7, d6 cd, Qxd6 QxQ, RxQ.. no).. I wonder whether he will see this - Ba3..? If I move my queen, opening the file for the rook - dangerous, as his bishop attacking on h6 will see my queen blocked in...- but he needs a couple of moves to get there.. its a nice trap, and black has so many problems to develop his pieces

That's the problem - 10 days since he last moved, and he has more than 200 games going..- this game long gone from the back of his mind, it is sooo easy to slip..

And black resigns.. Nb4, c3 c5, cxN cb, Bb2 Bc6 - despite being a Knight down, there is still some play in this for black. He pins the knight against the unprotected bishop on g2, threat of d5 removed, c-rack open for an attack, white's king's position weakened and open - I would have played on, but yeah, black probably have to many other games going to give this one the attention it will require..