When establishing tricks declarer must always be aware of the
"dangerous" opponent and play accordingly. Here is an example
from a recent team game.
SCORING: IMPs
Hand #32
Dlr
E
Vul
N-S
J943
104
J6
AK976
87
KJ982
K9872
10
A1062
765
53
QJ32
KQ5
AQ3
AQ104
854
West
North
East
South
Pass
1NT
Pass
2
Pass
2
Pass
3NT
All Pass
BIDDING: North used the Stayman convention to check on a spade
fit. With no luck there, his leap to 3NT was aggressive but this
was a team event and he did not want to miss a vulnerable game.
PLAY: West led a low heart and dummy's ten won the first
trick. Declarer saw a number of potential tricks but he could not
allow East in to lead a second heart so the only safe suit to attack
was diamonds. He led the jack from dummy won by West with the
king. West had no good exit card and finally returned a
diamond. It was now easy for South to knock out the spade ace to
establish his ninth trick. He ended up with two
spades, two hearts, three diamonds, and two clubs. At the other
table, West led a diamond instead of a heart and the contract was
defeated one trick.
Note that if South had first attacked either black suit, the
defense would establish five tricks before declarer had nine.