Kenilworth Kibitzer

1. e4 e5

2. Nf3 Nc6

3. d4 exd4

4. Nxd4 Bb4+ !?

This may look like a silly move compared to the classical 4...Bc5, because after the natural:

5. c3 Bc5     

black seems to have just lost a move.  However, as opposed to the classical variation (4...Bc5 5. Be3 Qf6 6. c3) that seems similar, the Black queen is not misplaced on f6.  The c3-square is still not available for the White knight on b1, so White is faced with the task of either proving that c3 is a useful move or to extract some other means of advantage from the opening.  I'll look at a couple alternatives in different posts, but let's start with the obvious and classical:

6. Be3 Bb6 (else 7. Nxc6)

There's an interesting 'Game of the Week' from Joel Benjamin on ICC that goes into some depth on this position which has become somewhat popular, though is not posing Black too many problems lately.  Also, there is a New In Chess article on the intermezzo check line in general that has the real cutting edge stuff, but for the rest of us I'll stick to basics.

White can play moves like 7. f4 or 7. Qg4, but the most popular (and not necessarily intuitive) move is:

7. Nf5            

This challenges Black's dark squared bishop while at the same time attacking the unprotected g7-pawn.  For some time the almost exclusive response was:

7.  ... BxB     after which the following is typical

8. NxB  Nf6

9. f3 O-O

10. c4 d6

11. Nc3

Where White has a position with some similarity to a Maroczy Bind setup, focusing on controlling d5, and possibly has a small edge.  However, Black has found an interesting way to combat this idea, meeting 7. Nf5 with:

7... g6!?

This move weakens the kingside, all the more so because Black's dark squared bishop is nowhere near the scene.  However, after the obligatory:

8. BxB axB

9. Nd4 Nf6

it's hard to see where White has gained anything by his last three moves.  Black is perhaps better developed, as the semi-open a-file, and developing pressure on the e-file.  This move may yet put the 7. Nf5 line out of business.  I will try to post some new ideas for White sometime later.