The <7. Nb5> variation did very well for White at master level around the beginning of the 20th century. See for example:

Janowski vs Teichmann, 1894

Eventually, retreating the Q to d8 was replaced by <Nb6> and <a6>, but in this game Swiderski probably plays the line in the best manner for Black. He counter-attacks on the Q-side and opens the <f> file, but he is still susceptible to a K-side attack.

Computer analysis suggests that by playing the extremely "concrete" move <13...g5!?> that Swiderski could have equalised:

click for larger view

If <14. fxg5> (14. f3!?) fxe5 15. dxe5 Ndxe5 16. O-O Nxf3+ 17. Rxf3 Rxf3 18. Qxf3 Ne5 =

I suspect that few masters of the time would have made so "weakening" a move as it went so against the general principles of the time - advancing pawns in front of your King in an area in which you are under attack.

Levin's <24. Ng5!> is a pretty move based on tactics.

<24...Qxg5> loses to <25. Nxd5!> Qh4 26. Rxf8+ Rxf8 27. Rxf8+ Kxf8 28. Nxb6

and ,

<25... Qxg5?> allows a mate in 3 <26. Qf7+ Kh8 27. Qf8+ Rxf8 28. Rxf8 mate.

Swiderski's natural <29... Ne4> is actually a blunder he needed to retreat his Bishop to <e8> to be rid of the <Nf7>. Keeping the Knight alive allows Levin to complete a mating net around Black's King with <31. Ngxh6+!!>

click for larger view

If <31... gxh6?> 32. Qg3+ Kh7 33. Rf6

The strength of Levin's attack is even more apparent in the unplayed variation

<32. Qf4!!> Nd5 (<32... gxh6?> 33. Qxh6+ Kg8 34. Qh8 mate) 33. Ng5+ and:

click for larger view

(i) <33... Kg6> 34. Qxe4+ Kxg5 35. Nf7+ Kh5 36. Qh7+ Kg4 37. Qh3 mate)