This 1940 chess composition by Prokes was in Practical Chess Endings by Irving Chernev. This book was emphatically espoused by the late NM Jim Gallagher of San Antonio,TX. Jim believed that far too many class players were deficient in the endgame phase of The Royal Game.
The idea behind the second rank skewer in this position is to advance the g6 pawn to g7 which places it on Black's second rank where the Black monarch also resides at c7. The Black Rook is then forced to attack the pawn from g6 to prevent its promotion to Queen.
White reacts with Ra1 setting up the skewer if the Rook captures the immune g7 pawn. This combined with the threat of Rook to a8 also threatening a Queen promotion is sufficient to force resignation.
Would like to close with a little tribute to the good old days in San Antonio chess when Selby Anderson was editor. Will close by listing some of the Players that I remember from that region: Martin Gordon, JP Hyltin, Eric Dimazana, Mitch Vergara, Mitchell White, Tony Alston, Greg Wren, Larry Moss, Steve Young, Pete Gibson, Enrique Rios, David John, Shawn Noland, Sonny Kamberi, Bill Wheeler, Jesse Matlock, Matt Campbell, Dave Mackey, John Hendricks, Paul Muljadi, Gregg Stanley, Steven Grubbs, Donald Flournoy, Randall Schwarz, ....