CLEARANCE - Scheveningen Variation of the Sicilian Defense - Early B7-b5 Systems

In both instances, very sharp and complex middlegame play ensues. Since White has omitted the defensive a2-a3 move, Black often has the b5-b4 counter-attack at his disposal. A lot of activity occurs on the critical a8-h1 diagonal, frequently leading to an exchange of pieces and both players must exercise caution in the resultant endgame. 

The Black player has one psychological advantage in the early b7-b5 systems: for the risk of starting a flank attack early in the game while the center is still fluid, the mathematical 'odds' are in his favor. Of the 600+ games collected in this compendium, Black won 42%, lost only 36% while 22% of the games were drawn. 

In his favor, the White player can usually maintain a lasting initiative, obtains the better piece development, and has a more secure King position.