The Dutch defense (1.d4 f5) goes through spates of fashionability in the chess world as a reply to White's 1.d4, with assessments of Black's chances wavering from excellent to inferior. Currently theory holds the White has the upper hand in the main lines which begin:
1.d4 f5
2.Nf3 Nf6
3.g3 g6
4.Bg2 Bg7
5.o-o o-o
6.c4 d6
The Dutch is a counter-attacking opening in which Black attempts to grab space on the kingside in preparation for an attack on White's king, or, alternatively, in which Black attempts to lock the white squares in the center, leaving White free to play on the black squares. As with most Black replies to 1.d4, it attacks the e4 square, preventing White from setting up the ideal pawn formation of pawns on d4 and e4.
The disadvantage of the move is that it does not advance Black's development (the only piece freed by the advance 1...f5 is the King, and a more accurate word than 'freed' might be 'exposed'). This gives White time to create a lead in development which he can use to establish a superiority in the center, which often transforms itself into a long-term strategic advantage. On the other hand, Black's attacking chances on the kingside can be very dangerous, and many tactical players have used the Dutch to try for a win with Black.