Cross-pins (1)
'Pen', 'attack on a pinned piece' and 'a pinned piece is a poor defender' are forms of pinning that were covered in the previous level.
The above forms were covered separately, but in this lesson they all reappear in a single move. We are introduced to a special form of the pin: the cross pin.
What should you do?
Win material or mate thanks to performing a cross pin.
The black bishop is partially pinned. The bishop cannot move across the a8-h1 diagonal, but action is possible across the a4-e8 diagonal. By attacking the black bishop with a new pawn, white can take advantage of the bishop's vulnerable position.
1.Qe4! pins the bishop (completely), because after 1...Bxb5 the queen is unprotected: 2.Qxb7. Also, white attacks a pinned piece and we can observe that a pinned piece is a poor defender (although the bishop looks at e4, it cannot capture the queen, because then black puts itself in check). White wins material.
This is a cross-pin over diagonals, i.e. a 'pure' cross-pin. In chess literature, this pin is also known as the St Andrew's Cross.
