Kennedy Variation, Riemann Defense

The Riemann Defense arises after 1. e4 Nc6 2. d4 e5 3. dxe5 Nxe5 4. f4 Nc6. White's fourth move hits the centralized knight with gain of time and adds a second pawn to the center. Black returns the knight to c6 rather than playing 4...Ng6, which is regarded as the main line. On c6 the knight does not attack f4, but it is safe from a later f4-f5 and covers d4 and e5, the squares White's pawns would like to use. The material is level, but White's e4 and f4 pawns form a mobile duo, and the half-open d-file is White's, while Black has the half-open e-file. That file lets Black aim pieces at the e4 pawn as long as White's king remains in the center.

White usually develops with 5. Nf3, by far the most common move. The bishop moves 5. Bc4 and 5. Be3 are less frequent alternatives, and both score slightly better for White in practice. The engine prefers 5. Nc3, Nf3 or Bc4 and rates White's position as a slight edge. White also wins clearly more often than Black across the games in the database. Black's task is to complete development quickly and hit back against the e4-f4 center before White can expand.