White to move
My move is the most accurate, although 52.Kh4 was also winning.
The half-second blunder.
How long does it take to notice that 53.Rxh5+ forces the king to move and allows 54.Rh7?
The point, which I could have worked out in half a minute, is that after 53.Rxh5+ Kd6 54.Rh7 Rxe7 55.Rxe7 Kxe7, White has a position with a single winning move. Moreover, I know this position well, having created a position almost identical for my Beginning Tactics exercises, which I am developing into a Kindle Book. In my exercise, White's pieces are down one square and the Black king is on e5.
White to move
56.Kg4! is the only move as it outflanks the enemy king. After 56...Kf6 57.Kf4 seizes the opposition, preparing for another outflanking maneuver further up the board.
The game continued:
53...Kd6 54.Kh4 Rxe7 55.Rxe7 Kxe7 56.Kxh5 Kf6 with a dead draw.
Of course, in such positions with limited time on the clock, it is possible to go wrong. We played another fifty moves as I offered my opponent the opportunity to err. He refused, playing precisely. Eventually, the game was drawn by repetition.
*Chess.com began hosting USCF online rated tournament in March 2015. I joined the group shortly after it formed, but did not play until two weeks ago. Last night was my third event. I won the event on tie-breaks over my opponent in this game. We both finished with 4.5/5.
**A nice feature of Chess.com that puts it ahead of sites such as LiChess.org is the recording of move times. Free Internet Chess Server (FICS) also records move times.