Martin's measurable dilator

Martin’s remarkable proof of ${\mathbf{\Pi }}_2^1$-determinacy from an iterable rank-into-rank embedding highlighted the connection between large cardinals and determinacy. In this paper, we isolate a large cardinal object called a measurable dilator from Martin’s proof of ${\mathbf{\Pi }}_2^1$-determinacy, which captures the structural essence of Martin’s proof of ${\mathbf{\Pi }}_2^1$-determinacy.