"Leaping into the breach" is an idiom that refers to taking charge to fix a crisis. Some synonyms to it include: "taking the bull by the horns", "stepping up", "rising to the occasion", "jumping in", "filling the void", "seizing the opportunity", "embracing the challenge", "assuming responsibility", "coming to the rescue", "answering the call", and "taking control". These phrases indicate a proactive approach towards addressing a problem by someone who is willing to take the lead and carry the responsibility of solving a crisis. Whatever phrase is used, it all boils down to being brave and confident enough to face a challenge head-on.