A normal trump fit consists of a combined holding of at least eight trumps in declarers hand and dummy. But it is well known that lesser holdings sometimes produce an excellent contract. This is particularly true of the four-three trump fit, known as a Moysian fit in honor of the late Alphonse Sonny Moyse, who published extensive analyses on the subject. The Moysian fit is often desirable when a weak side suit inhibits you from playing in notrump, as in todays deal.
After four routine bids, Norths three-heart bid showed exactly three hearts (with four he would have raised earlier). Norths previous two bids showed five diamonds and four clubs, so he was marked for a singleton spade. South correctly reasoned that a notrump contract would be difficult with the obvious spade lead, and he chose the Moysian fit.
West led the spade king and declarer quickly took advantage of dummys singleton: spade ace; spade ruff (with heart ace); heart to nine; spade ruff; diamond to king. The remaining trumps were drawn; but when the diamond finesse failed, declarer went down one. He still fared better than he might have at three notrump (likely down two), but he should have succeeded.
Moysian fits are delicate contracts. With only a slight superiority in trumps (seven to six) declarer must time the play carefully to keep things under control.
After winning the spade ace, declarer should immediately lead a low diamond to dummys jack if the finesse wins, great; but if it loses, there is no damaging return. East wins the diamond queen and might as well return a diamond (nothing really matters). Declarer wins the diamond king, ruffs a spade with dummys ace, draws four rounds of trumps (throwing clubs from dummy), then runs the diamonds. Declarer makes only one spade ruff, but altogether he wins 10 tricks and his contract.
© 1986 Richard Pavlicek