One of the many alternative defences to the Queen's Gambit. Instead of the Slav Defence (2..P-QB3), Black declines by 2..P-K3, 3..P-QB3 (move 3b, left), threatening to take and keep White's QBP soon after. Also known as the Half-Slav, it is in fact a "Slav-plus-K3" defence rather than a semi-defence.
Main play leads to the Meran Variation (Black's 6..QPxQBP, right) where Black begins to group rapidly on the queen's wing.