1.e4 e5 2.Nf3 Nc6 3.Nc3 Nf6
Judging by the advice often given to beginners "develop the knights before the bishops", the four-knights game should be the ideal opening. It was also quite popular at the beginning of the 20th century, but then lost many followers due to Rubinstein's gambit continuation 4.Bb5 Nd4. Interest only revived in the 1990s when the English grandmasters John Nunn and Nigel Short took up the opening. The most important, quite different options for White are 4.d4, 4.g3 and 4.Bb5.
4.d4 after 4...exd4 5.Nxd4 results in the Scottish Four-Knights (see the section on the Scottish).
The natural 4.Bc4, on the other hand, has no great significance, as it allows the simplifying fork trick 4...Nxe4 5.Nxe4 d5.
4.g3 - once just a footnote in theory books - is now a fully-fledged system, named after Igor Glek, who has played more than a hundred games with it since 1989. The line is similar to the g3 variation of the Vienna Game.
4.Bb5 is the Spanish Four Knights Game. Here Black can initially copy the moves with 4...Bb4 5.0-0 0-0 6.d3 d6, but after 7.Bg5,
which threatens 8.Nd5 is a good time to break the symmetry with 7...Bxc3.
The surprising 4...Nd4 bears the name of Akiba Rubinstein (1882-1961).
This move with an already developed piece may seem counter-intuitive at first, but 5.Nxe5 can be answered with 5...Qe7. The main variation is 5.Ba4, whereupon Black can sacrifice a pawn with 5...Bc5 6.Nxe5 0-0. Unfortunately, White can avoid these interesting complications with the undemanding 5.Nxd4 exd4 6.e5 dxc3 7.exf6 Qxf6 8.dxc3 Qxe5+ 9.Qe2 Qxe2+ 10.Kxe2, with a drawable endgame after only ten moves.
The four-knight game is very versatile. Some plays are more suitable for strategists, others will make tacticians feel right at home. Under no circumstances, however, should you underestimate this opening, which looks so simple at first glance.