Anyone who is inclined to underestimate Leonhardt’s playing strength should take a look at the following game in which he crushes Tarrasch:

However, Leonhardt's strong reply 19...Ne6! actually puts White in danger of losing, when the only try to maintain the balance is apparently with the exchange sacrifice 20. f4! Nf4! 21. Qg4! Nxh3 22. Qxh3 =.

In spite of it's impressive result in this game, Marshall's 20. Qg4?? is an outright blunder. Yet, Marshall maximizes resistance in the lost position and plays all the best possible moves, as does his opponent up until 24...Be7!?

Now 24...Be7!? might still win with difficulty, but Black could have scored a quick victory IMO with 24...Nf4!!

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[Position after 24...Nf4!! , Black missed in this game.]

After 24... Nf4!! 25. Be4 (25. Rd6 Rxg2+ 26. Kf1 Rxb2) (25. Bf1 Nxd5 26. Rxd5 Be7) 25... Ne2+ 26. Kf1 Rxe4 27. exf6 Bf5 , Marshall could have resigned.

if 20 Rxh7 there's no reason black won't take the rook and if 20 Bc1 Ne6! 21 Qd2(or Qe3) Rh4

I have Marshall's best games of chess and he didn't include this one in it.

Calli has a relevant point as to the score of the game. The Soltis score appears in the book "Lesser Known Chess Masterpieces 1906-1915" which is the book I looked at the game from.

To 24 ... Nf4 25 Bc4 Be6! looks strong.

Here's how I imagine the game felt to the players as it was unfolding. Leonhardt, by the way, was a world-class player, one of the top twenty in the world for a full decade, a very sharp tactician with a sense of positional correctness - after 12 moves of accurate defense, he would have felt he fully deserved the point, and would be appalled that Marshall is somehow still clawing his way to victory.

14....a6 is a bit of a strange choice. Marshall's ambitions are on the kingside not the queenside. After this move, he must have felt that he was in a Marshall position and tactical possibilities would start to appear on the board.

18.e4!? is the kind of shot that Marshall made his living on: 18....fxe4 19.Nxe4 dxe4 20.Bc4+ and now the center and kingside are rolling.

But Leonhardt has 19....Ne6! I have a feeling Marshall missed or underestimated this and suddenly it looks resignable for white. e4 and f4 are hanging and the trick with Bc4 no longer works after ....dxe4.

Marshall puts together Adolf Anderssen-esque combination with 20.Qg4?! It's fundamentally unsound - 20.f5 sacrificing an exchange is a better way to continue - but this is the kind of combination that once you see it, it's very difficult not to play it.

It's rare to be able to sacrifice queen, rook, and knight on one move as Marshall does with 21.Rxh7! If 21....Kxh7 22.Nf6+ Bxf6 23.Qxg6+ Kh8 24.exf6 with f7+ coming.

I played through the combination to 24.Rxd5 and was sort of surprised to realize that for all his trouble Marshall is just down a piece. Leonhardt must have felt that he'd weathered the storm and could consolidate easily. Contrary to what some of the kibitzers were saying, 24....Be7 is a perfectly reasonable move. 24....Nf4 25.Bc4 Be6 26.Rd6 is just an alternative.

But after 24....Be7 it looks resignable again for white: he's down a piece for a pawn and the rook is precarious on d5. 25.h3 looks like just a swindler-type move to disrupt black's pieces. The computer finds 25....Bb7 here although that's a hard move to make. There are complications with 26.Bc4 Rxc4 27.bxc4 Bxd5 28.cxd5 with a pawn roller or 26.Rd7 Rxg2+ 27.Kf1 Rxb2 28.Rxe7 with threats against g6 and e6. In a real game, I might well have played 25....Rg3 and just given up the rook for white's light-squared bishop.

But Leonhardt has good reason to play the way he does because 26....Nf4 looks like a killing shot - resignable again for white.

Now white has a brand-new round of sacrifices with 27.Rd8+!. Again, this is not so terrible. The attractive-looking 29.e6+ Kxg6 30.e7 doesn't work: after 30....Ne2+ 31.Kf2 Re4 32.e8=Q Rxe8 black just gives the rook back and once again is up a whole piece in the endgame.

After 30.Rxa8 Leonhardt was probably congratulating himself. He'd played really good defense, made it through several waves of attacks, and reached an endgame where Marshall has only two pieces left. 30....Bd3 is a blunder but an understandable blunder - he wants to hold onto the a6 pawn and psychologically he must have been feeling that he deserved a moment to consolidate. 30....Kf7 isn't so simple. After 31.Rxa6 it's three pawns for a piece, and white's kingside pawns look dangerous.

But with 30....Bd3? it turns out that Marshall still has tactics and the e-pawn gets down the board in three moves.