Trainer

In 1935, Schlage became Reichstrainer des Großdeutschen Schachbundes (Chief Trainer of the German Chess Federation). Together with Alexander Alekhine and Efim Bogoljubow, he trained the German national team for the 3rd unofficial Chess Olympiad at Munich 1936. In August 1939, he trained the best young German players (Klaus Junge (15 years old), Wolfgang Unzicker (14), Edith Keller (17), Karl Krbavic (17), Rudolf Kunath (15), etc.) in Fürstenwalde (Jugendschachwoche).^[13]

Roesch vs. Schlage, 1910

Roesch vs. Schlage, 1910

	a	b	c	d	e	f	g	h
8									8
7									7
6									6
5									5
4									4
3									3
2									2
1									1
	a	b	c	d	e	f	g	h

Position following 13...Bh3, shown as the starting position in the film 2001. Both the real game and the fragment depicted in the film concluded 14.Qxa6 Bxg2 15.Re1 Qf3 0–1.

In 1910 in Hamburg, Schlage defeated Roesch in a 15-move miniature which opened with the Ruy Lopez; the game was later reproduced in a 1955 collection by Irving Chernev.^[14] In the 1968 film 2001: A Space Odyssey, a HAL 9000 supercomputer is shown defeating astronaut Frank Poole at the conclusion of a game, with moves and board positions identical to the conclusion of the Roesch–Schlage game. Chess writers have therefore attributed the film's game to Schlage's.^[15][16]

Schlage vs. Ahues, 1921

Schlage vs. Ahues, 1921

	a	b	c	d	e	f	g	h
8									8
7									7
6									6
5									5
4									4
3									3
2									2
1									1
	a	b	c	d	e	f	g	h

White to move and win

A frequently reproduced endgame problem is attributed to a game played by Schlage (White) and Ahues (Black) in Berlin, 1921.^{[lower-alpha 1]} Schlage had an opportunity to win, but he blundered with an incorrect king move, at which point Ahues was able to force a draw. The position has been discussed by Ilya Maizelis and Paul Keres, and later by Bruce Pandolfini and Jesus de la Villa.

Each player has two pieces: one pawn and one king, with White to move. The pawns block each other's paths, unable to move of their own accord, and the kings are posted at nearly equal distance from this deadlock. Each king must advance toward the deadlocked pawns, either with the aim of capturing the opposing pawn and thus clearing the way for promotion (thereby securing a win), or else by frustrating this design and thus denying the opponent a win, forcing a draw. At this point, the continuation actually played was 1.Ke6 Kc3 2.Kd6? Kd4 3.Kc6 Ke5 4.Kb7 Kd6 5.Kxa7 Kc7 ½–½.^{[19][20][21][22]} Once the black king occupies the critical c7-square and corners its white counterpart, it forces a draw, whether by threefold repetition, stalemate, or agreement. White should instead have played 2.Kd5!.^{[19][20][21][22]} With this move, the white king has just enough time to secure all the requirements for a win: capture the black pawn, get out of its own pawn's way, prevent Black from accessing the c7-square, and prevent Black from recapturing the white pawn.^{[lower-alpha 2]}

When presented as a problem, there are two points about the position. First, players can make tactical use of the fact that kings can never occupy adjacent squares—a king can never move into check. By moving one's king next to a square, the opponent's king is prevented from moving to that square on the following move. This technique is referred to as "bodychecking",^[22] or "shouldering".^[23] By playing 2.Kd5!, White forces Black to make a waiting move at some point, which loses time and fails to access c7. Second, the geometry of the chessboard—and the movement of the pieces—is non-Euclidean:^[24] a king can follow advantageous diagonal paths and still reach a given square in the same number of moves as if it had moved along a "straight line" in a given rank or file.^[25]

1979 Mali chess stamps

In 1979, the African country Mali issued a quartet of stamps depicting chess masters; Alekhine, Bogoljubow, and Schlage were represented, together with Dawid Janowski. Tim Krabbé found Schlage's inclusion among much stronger players to be incongruous and suspected that the stamps were designed by a German, on account of the individuals' roles in German chess during the war (although Janowski had died in 1927). A correspondent later informed Krabbé that the stamps were executed by a French designer.^[12]