Kiel Variation

The Kiel Variation arises in the Marshall Variation of the Modern Scandinavian when White chases the d5 knight with 4. c4. Instead of the usual retreats 4...Nb6 or 4...Nf6, Black sends the knight forward to b4, where it eyes c2 and d3 and invites White to overreach. The point is a trap. After 5. Qa4+ N8c6 6. d5?, the reply 6...b5! gives Black a good game. Harman and Taulbut call the line speculative, and with accurate play White keeps a large advantage.

The main refutation is 5. a3, the most popular choice, which drives the knight away. Play continues 5...N4c6 6. d5 Ne5, and then White plays either 7. Nf3 or 7. f4 Ng6 8. Bd3 e5 9. Qe2. White also does well with 5. Qa4+ N8c6 6. a3!, avoiding the premature d5. Engines rate White clearly better, and White scores well after 5. a3. In online games, however, Black has scored heavily after 5. Qa4+ and 5. Nc3, which shows how easily the traps work in practice. The variation is seldom seen at a serious level.