The Steinitz Defence Deferred ("ECO" C79) also called Russian Defence. With the move order 3...a6 4.Ba4 Nf6 5.0-0 d6, Black waits until White castles before playing ...d6. This can enable Black to avoid some lines in the Steinitz Defence Deferred in which White castles although the position of the knight on f6 also precludes Black from supporting the centre with ...f7–f6. These nuances seem to have little importance today, as neither the Steinitz Defence Deferred nor the Russian Defence have been popular for many years.