From Chesspedia, the Free Chess Encyclopedia.
The Dunst Opening is a chess opening where White opens with the move (see algebraic notation):
This fairly uncommon opening may have more names than any other: it is also called the Heinrichsen Opening, Baltic Opening, van Geet's Opening, Sleipner Opening, Kotrč's Opening, Meštrović Opening, and the Queen's Knight Opening. The names Heinrichsen and Baltic derive from Lithuanian chess player Arved Heinrichsen (1876–1900). The opening was also analyzed and played by the New York master Ted A. Dunst (April 11, 1907 New York City–December 18, 1985 Lambertville, New Jersey), giving the opening its most popular name in the U.S. The Dutch International Master and correspondence grandmaster Dirk Daniel ("Dick D.") van Geet (b. March 1, 1932) frequently plays 1.Nc3, so it is often called the van Geet's Opening in the Netherlands. The appellation Sleipner seems to come from Germany. Sleipner is Odin's (Wotan in German) magical eight-legged horse, and chess knights are horses with up to eight different possible moves each turn. Czech Jan Kotrč (1862–1943), editor and publisher of the magazine České Listy, said the opening was analyzed by English players. Zvonimir Meštrović (b. October 17, 1944) is a Slovenian International Master who often adopts this opening.
1.Nc3 develops the knight to a good square where it attacks the central e4 and d5 squares. Although quite playable, 1.Nc3 is only the eighth most popular of the 20 possible first moves. The third-ranking 1.Nf3 is more than fifty times as popular. Some very strong correspondence chess players employ 1.Nc3 frequently, and it is also occasionally seen over-the-board.
The reason for 1.Nc3's lack of popularity is that while 1.Nf3 prevents 1...e5, 1.Nc3 does not prevent 1...d5. After 1.Nc3 d5, Black threatens to chase the knight with 2...d4. White can prevent this with 2.d4 but he obtains a somewhat inflexible position in the Queen's Pawn Game with his knight blocking the c-pawn. More often, White plays 2.Nf3 (and if 2...d4, 3.Ne4), a sort of Black Knights Tango with an extra move, or 2.e4 (intending 2...d4 3.Nce2). If White allows his knight to be chased away in this manner, he cedes a spatial advantage to Black, although he might work to undermine this along the lines of hypermodernism. Also possible after 1...d5 is the trappy "coffeehouse" line 2.e3 e5 (other moves are also playable, of course) 3.Qh5!?, e.g. 3...Qd6 (3...Nc6 4.Bb5) 4.d4 exd4 (forced) 5.exd4 c6 (5...Nf6? 6.Qe5+! Be6 7.Nb5; 5...Be6 6.Nb5 Qb6 7.Bf4) played in offhand games by the Danish master Ove Kroll.
It is considered an irregular opening, so it is classified under the A00 code in the Encyclopaedia of Chess Openings. Transpositions to more common openings are possible. For instance after 1.Nc3 e5 2.e4 we have the Vienna Game and 1.Nc3 d5 2.e4 reaches a position in the Center Counter Defense, or Alekhine's Defense if Black plays 2...Nf6. The Dunst can also transpose into variations of the Sicilian Defense (closed), Queen's Pawn Game, French Defense, Caro-Kann Defense, and Scotch Four Knights Game.