6 . ▁( The ▁move ▁ 8 . Q f 3 , ▁popular ▁in ▁the ▁nin ete enth ▁century ▁and ▁rev ived ▁by ▁E f im ▁Bog ol jub ov ▁in ▁the ▁tw enti eth , ▁can ▁be ▁played ▁instead ; ▁Black ▁may ▁reply ▁with ▁ 8 ... h 6 , ▁ 8 ... R b 8 , ▁or ▁ 8 ... Be 7 .) ▁White ▁then ▁has ▁a ▁choice ▁of ▁retre ats ▁for ▁the ▁kn ight . ▁The ▁usual ▁move ▁here ▁is ▁ 9 . N f 3 , ▁after ▁which ▁Black ▁obtain s ▁some ▁initi ative ▁after ▁ 9 ... e 4 ▁ 1 0 . Ne 5 ▁Bd 6 ▁( see ▁diagram ). ▁This ▁is ▁the ▁Kn or re ▁Vari ation , ▁and ▁is ▁considered ▁to ▁be ▁the ▁main ▁line ▁of ▁the ▁Two ▁Kn ights ▁Def ense . ▁After ▁ten ▁moves , ▁White ▁has ▁developed ▁only ▁two ▁pieces ▁against ▁Black ' s ▁three ▁pieces ▁and ▁pa wn s , ▁but ▁has ▁an ▁extra ▁pa wn ▁as ▁well ▁as ▁a ▁better ▁pa wn ▁structure . ▁Both ▁ 1 1 . d 4 ▁and ▁ 1 1 . f 4 ▁have ▁been ▁tried ▁here ▁with ▁no ▁definit ive ▁conclusion . ▁ 1 0 ... B c 5 ▁is ▁a ▁vi able ▁alternative ▁for ▁Black , ▁as ▁is ▁ 1 0 ... Q c 7 ▁( the ▁G oring ▁Vari ation ). ▁ ▁Ste init z ▁fav ored ▁ 9 . N h 3 ▁instead , ▁although ▁it ▁did ▁not ▁bring ▁him ▁success