The Nimzo-Indian Defence (E20-E59) is a chess opening characterised by the moves: 1. d4 Nf6 2. c4 e6 3. Nc3 Bb4. This hypermodern opening was developed by Grandmaster Aron Nimzowitsch who introduced it to master-level chess in the early 20th century. Unlike most Indian openings the Nimzo-Indian does not involve an immediate fianchetto, although Black often follows up with ...b6 and ...Bb7. By pinning White's knight Black prevents the threatened 4.e4 and seeks to inflict doubled pawns on White. White will attempt to create a pawn centre and develop his pieces to prepare for an assault on the Black position.
Black's delay in committing to a pawn structure makes the Nimzo-Indian (sometimes colloquially referred to as the "Nimzo") a very flexible defence to 1.d4. It can also transpose into lines of the Queen's Gambit or Queen's Indian Defence. The Nimzo-Indian is a highly respected defence to 1.d4, is played at all levels and has been played by every world champion since Capablanca. White often plays 3.g3 or 3.Nf3 to avoid the Nimzo-Indian, allowing him to meet 3.Nf3 Bb4+ (the Bogo-Indian Defence) with 4.Bd2 or 4.Nbd2, rather than 4.Nc3.
Nimzoroy plays the Nimzo-Indian against my d4 in this game:
I opted for the rarely played Sämisch Variation with move 4.a3. According to Wikipedia, this variation (named after Fritz Sämisch) is a direct attempt to refute Black's strategic concept, as White gives up a tempo and concedes doubled c-pawns to gain the bishop pair. After 4...Bxc3+ 5.bxc3, Black has several possibilities, the most common of which is that he immediately begins to blockade the doubled pawns with 5....c5 and applies more pressure on the (often doomed) pawn at c4 with the moves ...Ba6, ...Nc6-a5 and ...Rc8. In the early days of this line, 5....d5 was frequently played, though it was soon realised that this enabled White to liquidate the weakness at c4, so the idea fell from favour, particularly after the game Botvinnik-Capablanca, AVRO 1938, and has never been revived at top level. As compensation, White establishes a powerful centre, in order to play for a kingside attack before Black can make use of his static advantages. White has two main options for playing: he can move slowly into the centre with 6.e3, or he can play 6.f3, followed by 7.e4 to take a quick hold in the centre. In practice, however, Black has demonstrated that White's structural weaknesses are more serious than the attacking chances he gets, so this variation is rarely seen nowadays. The Sämisch Variation was employed five times by Mikhail Botvinnik against Tal in the 1960 World Chess Championship, with five draws resulting, and once in the 1961 rematch, with a win for White.
We were following the book moves in this variation up to move 10. On move 11, I decided to deviate and played a dubious move 11.Nh3 instead of 11.Be3, then sacrificed two pawns, ignored the threat on my bishop and rook on a1 and sacrificed my knight with Nxf7. The game is shown below using NimzoRoy's favorite club set in the diagram: