Zwischenzug

A zwischenzug — an 'in-between move' — is a surprise move you slip in during what looked like a forced sequence, usually a check or a bigger threat, before making the expected recapture. It can flip the result of the whole exchange in your favour. Always look for one before you recapture.[Chess.com — Zwischenzug chess term]

Source for further study: Aagaard, Attacking Manual 2; Chess.com — Zwischenzug chess term.