  We study the question of $\mathcal{L}_{\mathrm{ring}}$-definability of
non-trivial henselian valuation rings. Building on previous work of Jahnke and
Koenigsmann, we provide a characterization of henselian fields that admit a
non-trivial definable henselian valuation. In particular, we treat cases where
the canonical henselian valuation has positive residue characteristic, using
techniques from the model theory and algebra of tame fields.
