The Vienna coup is an unblocking technique in contract bridge

Contract bridge

Contract bridge, usually known simply as bridge, is a trick-taking card game using a standard deck of 52 playing cards played by four players in two competing partnerships with partners sitting opposite each other around a small table...

, so called because it was first recorded in Vienna in the days of whist

Whist

Whist is a classic English trick-taking card game which was played widely in the 18th and 19th centuries. It derives from the 16th century game of Trump or Ruff, via Ruff and Honours...

, used to avoid problems when executing an automatic squeeze.

Examples

Take this sample hand, below.

On the play of the A East is squeezed, but can escape by throwing a small heart. Although the Q is set up, there is no way back to the hand to cash the winning heart.

But look at the hand after the 2 is played to the A.

Now on the play of the A East finds no escape. Unless he discards the K the spades will be set up.