～ばこそ

～ばこそ is a strong, formal pattern used to emphasize that a certain reason or condition is the very cause or prerequisite for something. It often contrasts with other possible reasons, underscoring that X is exactly why Y happens. It appears in written or formal speech, and in careful, persuasive contexts where the speaker wants to highlight the necessity or exclusivity of the given reason. Use it when you want to stress that the circumstance is not just a contributing factor, but the key reason. Typical triggers include adverbial or noun phrases that set up a clear cause, followed by こそ-less common after からこそ or こそ following a conditional form. The form is relatively formal and literary, so it’s less common in casual conversation.