If anyone thinks that this tactical theme <USING CHECKS TO REPOSITION YOUR PIECES WITH GAIN OF TIME TO MEET THREATS>. is too obvious or trivial, note that Topalov has overlooked it not once but -twice- this year.

In his game against Svidler at Corus, Topalov (Black) missed the defensive repositioning of the White queen via the manoeuvre ♕g3-b8+!, ♕b8-b4.

And then at Linares against Carlsen, Topalov (Black) resigned in a drawn position(!) because he failed to see the defensive manoeuvre ... ♕d7-d5+, ... e6-e5, ... ♕d5-g8 to meet the threat of a White queen invasion to h8.

The lesson to be learned from both of these Topalov oversights is that a piece may be repositioned with <GAIN OF TIME> by <CHECKING> the exposed enemy king (♕g3-b8+!, ... ♕d7-d5+) to meet a threat that otherwise seems either impossible or very awkward to meet.