"To break a promise" means to not do what you said you would do. It is not keeping your word or failing to fulfill a commitment that you made to someone. Full definition
If the club hadn't of broken their promise of us signing the elite and challenging the very biggest, I wonder if maybe it could have gotten us back into the game. (justarsenal.com)
Breaking a promise on tuition fees doesn't count. (politics.co.uk)
Try to keep your word, and when you can't, apologize for breaking a promise. (babycenter.com)