Removing the Defender
I find many tactics and combinations go together hand-in-hand. For example the tactical concept I am talking about here, removal of the defender, ties into my article on why counting is futile.
Removing the defender, also known as undermining, is the tactic in which you capture the piece defending a piece that is under attack with the plan of subsequently taking the now undefended piece.
The position below displays a good example of undermining. At first the knight on f2 appears to be properly defended. However when white trades queens, black is forced to recapture, at which point the knight on f2 is no longer defended, and white captures the knight and is left with an easily won game.