In contract bridge, an underruff is a play in which declarer ruffs a trick and a defender deliberately ruffs with a lower-ranking trump. This is a counter-intuitive maneuver which, on rare occasions, may offer some critical benefit to the defense.


Example

The late writer Alan Truscott (1925 - 2005) wrote several articles about the underruff for The New York Times. In this deal, Italian world champion Benito Bianchi declared 6H and received the opening lead of the D9:1

North
AQ105
84
WestAJ8642East
K9478732
J96253
93SouthK107
KJ42SJ6Q863
HAKQ107
DQ5
CA1095


"Bianchi won the diamond lead with the ace in dummy, entered his hand with a club to the ace and led the SJ. West was forced to cover with the king, and South won with the ace and continued the suit. On the third round he discarded the DQ, and was able to ruff a diamond and ruff a club. He then ruffed a diamond with the HQ and ruffed another club to reach this position:

North
5
WestJ86East
8
J96253
South
SQ
HAK10
D
C10


"Playing dummy's S5 and throwing the C10 now did the trick. West was forced to ruff his partner's winner and lead from the HJ.

"West had missed the chance for a very remarkable defense indeed. Instead of discarding a club when the third round of diamonds was ruffed he should have underruffed with the H2. He should then have unblocked his CK, leading to this ending:

North
5
WestJ86East
8
J9653
South
JSQ
HAK10
D
C10

"The DJ is led and East ruffs. South ruffs with the HK, and West must pass the final test. If he underruffs for the second time, he defeats the slam."


References

1Truscott, A. (1985, August 4). An Underruff Defeats a Slam. The New York Times.

See also

  • Trump Promotion
    Any defensive play that "promotes" a trump holding into an extra winner.

  • Uppercut
    A trump promotion that occurs when the defense ruffs a trick and forces declarer to overruff.