A wise man from San Antonio laughed when he heard I was playing fourth suit forcing. He answered my curious look by saying, “When is bidding the fourth suit not forcing?”
I thought about it, and it often is forcing one round but not always to game.
The fourth suit forcing convention can be played forcing one round or forcing to game. I like it forcing to game. Whether you use this convention or not is not important but understanding the underlying principle is important.
When one is weak and has no fit with partner, one tries to exit the bidding as soon as possible. Busy auctions and especially those where the fourth suit is mentioned are almost always forcing.
In the auction where all four suits are mentioned at the one level, one spade is naturally one round forcing. A jump is not needed.
Fourth suit forcing can also suggest an interest in slam when the partner using it could have signed off in game.
The bidding: South, with 13 points, opens one club. West has six hearts but the heart suit is not good enough being vulnerable. King empty may be fine when not vulnerable.
North bids his diamond suit and South replies one spade. North has an opening hand opposite partner’s opener, so he bids two hearts forcing to game. If he had a heart stopper, he could have bid 3NT. Therefore, the fourth suit may imply no stopper or the desire to explore possible spade and diamond fits.
As it turns out, neither North nor South can bid notrump because of a lack of heart stoppers. North gives a delayed raise of spades so South knows a Moysian fit (4-3 fit named after Alphonse Moyse Jr.) is likely. Their spades are strong and they have a secondary diamond fit, so South tries four spades.
The contract: Four Spades by South
The opening lead: The six of hearts, fourth best
The play: East wins the opening lead, and seeing a singleton heart in dummy, leads trump. South has to drive out the ace of clubs, check on diamonds and ruff a heart before drawing trump. It is very important that South leaves the trump in dummy to take care of any heart lead. If he ruffs in his hand, South will have less trump than East and will likely lose control of the hand. West holds up with the ace of clubs once, wins the club continuation and then plays a third club hoping East can ruff. South wins in his hand and ruffs a heart in dummy.
He then overtakes the king of spades and draws trump in his hand. If the diamonds split two-two, he makes five spades. If the queen is protected, he makes four spades.
The result: Four Spades making five for +450.
Note: Had South decided that a club ruff was risky, he could have seen that diamonds were setting up with trump still in the dummy.