Strictly speaking the Bd3-e2 manuver doesn't lose a move, since black also moves his QB twice.

Judging from Opening Explorer, 9 Nf3 has continued to be the normal continuation, with 9...Be7 as the most popular continuation and 9...Bg4 as the second most popular. So much for Tartakower and Du Mont. Black seems to score well in the main line of the Four Pawns. I have played 6...c5 on the few occasions I've had the opportunity -- maybe I should reconsider?

<I still have clearly in mind the impression made upon me by one of his games against his constantly outshone rival, Dr Tarrasch. Lasker never paid excessive attention to the theoretical studies of his compatriot Dr Tarrasch, firstly because he was a basically practical player and secondly because Lasker did not attribute to these studies more importance than they deserved. Nevertheless, on a particular occasion he slipped into an inferior position to which Tarrasch induced him and suddenly found himself at his rival’s mercy. It was then that Lasker showed his fighting spirit. Instead of making the ordinary move which would have occurred to any other master, whereby he would sooner or later have lost or, with difficulty, drawn, Lasker sacrificed a pawn. But what a sacrifice! I have seen no such sacrifice in any modern games! It was impossible to know whether it should be accepted or refused. As the saying goes, “it shook the board”. Here was the “eccentricity” of the old teacher of philosophy and mathematics of the University of Breslau who took his opponents by surprise. The result was that after a few moves it was Lasker, not Tarrasch, who had the better game. This game shows any chessplayer the extraordinary quality of play, which he possesses even today as a glorious septuagenarian, of Dr Emanuel Lasker, world champion for 25 [sic] years.>

<Lasker’s opponents often attributed their reverses to a single move – “If only I hadn’t played that blunder.” This thinking served Lasker well by leading his rivals to misleading conclusions about what they did wrong. They didn’t recognize how many little mistakes, how many minor turning points were hidden in the game.

In the following game, the last between these two great rivals, Tarrasch obtains a huge edge by move 14, which he slowly enlarges. Then something goes horribly wrong. But it was difficult to say what. most annotators can only find one of Black’s moves to criticize (“24…Qf5?”) and only a few good moves by White.

In reality, there were several pivotal moments. First Lasker managed to halt the momentum of moves 10-14. That improved his situation from “about-to-lose” to “not-losing-now.” It took several more moves to arrive at the next level, “not-losing-at-all” and still more to reach the status of “might-win.”

After 10. Bd3?

Lasker's 9th move was new and this one is just bad.

After 10...Bg4!

And this is why. Giving up the pawn (11. 0-0 Nxd4) is unsound but 11. a3 was worth trying.

After 13...Qf4.

Black has reached what later became a book position -- but with an extra ...Bb4. Without that move the position is considered roughly equal after (13) Qc1 Qxc1+.

However, with the extra tempo Black has the initiative whether he goes after the d-pawn (...0-0-0) or plays against c4 (....Na5). For example, 14. Qc1 is met by 14...Qxc1+ 15. Rxc1 0-0-0 and then 16. a3 Bxc3+ 17. bxc3 f6 with a small edge.

After 14. Rg1? [the pawn sacrifice Capablanca praised so highly]

Characteristically, Lasker defends the d-pawn tactically (Rg4). But better was 14. a3 Bxc3+ 15. bxc3.

After 16....Qg2

Tarrasch had allowed Lasker to escape too many times in the past. A "luck scoretable," mimicking what he composed at Nuremberg 1896, would reveal at least a plus-five for Lasker in his games with Tarrasch. That may explain why he passes up the Q-sack that a modern GM would love -- 16....Qxh4!? 17. Bxh4 Rxd4 18. Qb3 Rxh4 19. 0-0-0 Rd8 or 19....Rd2.

After 21...Bg5.

White is a move or two away from disaster. He can't play normally because 22. Ne4 Be3 or 22. Bd3 Nxd4 cost material.

After 22....f6

So far the game has been all Tarrasch. His move is intuitive but misses a nice finesse, 22....Bc1!. White has nothing better than 23. Qc2 after which 23....Be3 trades off the bishop that holds his position together (24. Qe4 Bxf2+ 25. Kxf2 f5!).

After 23....Qxf6

Against any other opponent Tarrasch might have considered 23...Bxf6 more seriously, in light of 24. Qxe6+ Kb8 or 24. Be3 g5 25. Qxe6+ Kb8 26. Ne4 Rhf8. But these lines seem to leave White with too many drawing chances. And that answers the question that puzzled Tarrasch at St. Petersburg [namely, why opponents played weakly against Lasker]. Masters often played weakly against Lasker because he wasn't just any other opponent. The possibility of beating a world champion or even an ex-champion raised the emotional level beyond what many found comfortable, or even tolerable. They pressed too hard.>

<After 24....Qf5

Black decides he can't mate after all. This move was widely denounced, but that's a bit unfair. [Indeed, Tartakower and du Mont claimed this move lost the game.] Black still has a winning position in the endgame. But a quiet alternative such as 24...Kb8 would serve much better.

After 26. Bd3!

Black may have been counting on winning the d-pawn after 26…Bf6 (or inflict 27. d5 Bxc3+ damage). But because 26…Nxd4? loses to 27. Bxd4 Rxd4 28. Bxf5+, White buys time for Nd2 and f3-f4!

After 27….h4

White has gotten past about-to-lose – but he should still lose eventually. Trading bishops is still the smoothest win, e.g. 27…Rhe8! 28. Kf1 Na4 29. Rb1 Be3!.

After 31. Kf1

White signals that he has survived. This move says that he can just try to improve the placement of his pieces (Nd4-e6) and wait for Black to prove that he is winning.

After 31…Nbc8?

Tarrasch didn’t respond well when confronted with unexpected obstacles. His best games were linear – an opening advantage grew logically and steadily until, by move 30 or 35, it had become overwhelming.

In this game his edge was growing until move 22 or so and seemed to be only a few good moves away from becoming unstoppable. But now he sees he’ll need more than a few good moves. He needs a pawn-break, eitehr from …b5 or …c6. And he sees that 31…c6 can be answered by 32. d6!, after which 32…Rxd6 33. c5 Rxd3 is dubious (34. Rdxd3 Nbd5 35. Bd4).

Nevertheless 31…Na4! and 32…c6 would get him closer to a win, e.g. 32. Nd4 c6 33. Ne6 Nb2.

After 32….c6?

Black insists. He would still have a serious edge after 32…Nb6 33. Nd4 Na4 or 32…Nd6 and …Ne4. For example, 32….Nb6 33. Nd4 Ne4 34. Bxe4 fxe4 35. Ne6 Rd7 36. Re3 Nf5! and then 37. Rxe4 h3 38. Kg1 Nd6.

After 34…Ka8

Black loses this game because he is too concerned with keeping his material edge. The tide turns after 34…Kc7 35. Nd4 Bxd4 36. Bxd4 Rh7 37. Be5+ Kd8 38. Rb8, intending 39. d6 and wins. But Black could save himself wth the 36….cxd5! exchange sacrifice.

After 35. Nd4! Bxd4?!

White has an attack, but it can be handled by 35….Rd7 36. Nxc6 Nxc6 37. dxc6 Rc7.

After 38…Nb7?

A knight on b7 is always bad, Tarrasch might have said. It was widely believed that White still has a clear advantage after 38….Ne4 39. Bxe4 fxe4 40. Rhb3 followed by Rb8+ or Rb7.

But the simple 40…a5 holds because of 41. Rb7 cxd5 42. Bb8 Nf5! and then 43. Rxh7 Rxb8, when Black can again think about winning.

No better is 39. d6 because of 39…Nd2+ 40. Ke2 Nxb1 41. dxe7 Rxe7 42. Bxb1 g5.

After 40. Rc1

After his minor errors at moves 24,, 27, 34 and 35 and the major ones at moves 32 and 38, Black’s position has fallen into the can-lose category. Some observers felt it was much worse than that. Teichmann though Black was “hopelessly lost” three moves ago.

40….Rf8?

But this is the decisive error. It’s common sense, Lasker might say, that Black should use his badly placed knight (40…Na5!) rather than reposition the other one.

After 44. Rce1!

The rooks rule (44….Rd8 45. Re7!).

After 45…Kb8

However White threatens not only f4, (for example 18...Rd7 19 f4 Qg6 20 Qxg6 hxg6?? 21 Rxh8+) but also d5 in the event of ..Rd7 when ...exd5 will invite the pin Bh3, for example 18..Rd7 19 f4 Qe7 20 d5 Bxc3 21 Qxc3 exd5 22 Bh3.

Tarrasch got a great position out of 11....Bxf3 -- check the notes I posted. ...Bxf3 is a standard idea in this opening, trying to undermine the pawn on d4 and take advantage of White's loose kingside.

Presumably he played the second exchange, 35....Bxd4, because he thought it was his best defensive chance. Tarrasch was a great player, of course, but I don't think defense was his forte, especially when he felt he'd messed up a good position. He tended to make huge concessions that weren't completely necessary.

Here are a couple of other examples of him not defending well against Lasker.

Tarrasch vs Lasker, 1908

birthtimes is right that 42.c6 is crushing. But if 42.Bb8 Nf5, instead of taking the rook on h7 White plays 43.R7b6! threatening Ra6+, and Black has no defense.