1. c2c4  1... e7e6  2. b1c3  2... d7d5  3. d2d4  3... g8f6  4. c4d5  4... e6d5  5. c1g5  5... f8e7  6. e2e3  6... h7h6 The Queen's Gambit Declined is probably the classical defense that has changed the most in recent years, with new plans for the black side being discovered.