As both Militia and Masquerade are terminal Actions, you will need a +Actions card to play both of them together (e.g., Village, Festival, Shanty Town).

This is an especially cruel combo that baits your opponent into discarding his bad cards before forcing him to pass one of his remaining cards to you.  While it doesn’t have quite the sting of a Possessed Ambassador (since your opponent will usually discard Victory cards rather than holding onto them), it can turn Masquerade into a much stronger attack than usual.

Naturally, Goons can be substituted for the Militia.  Torturer can as well, but beware of playing Masquerade when your opponent chooses to take the Curse instead of discarding!