Game-forcing 2-over-1, which is part of the American standard, is emerging in France where it is given overwhelming support by its champions as it makes sequences more natural. But it imposes changes to the old system, especially for the 1NT response.
In the French system, a 2-over-1 jump take-out is forcing for one round, auto-forcing but not game-forcing. That now belongs in the past. The system that you will play or are already playing is not only more efficient, but it also adapts to the one used with your partner without any difficulty. It is now forcing to game. As soon as you respond 2♣ over 1♠ or 2♥ over 1♠, you can no longer stop below game.
The 1♦-2♣ sequence must also become game-forcing, still looking for better efficiency easily, but will not be covered in this article (take patience). Let us start by recalling in which sequences and conditions you can – sorry, you could – stop below game.
I-1 Non-forcing sequences
Three sequences, if allowed by Opener’s rebid:
11 HCP, two cards in Spades with no stopper in Hearts.
11 HCP, one stopper in Hearts, a more or less balanced hand.