There is a sexual joke at Ach. 591–2:

Kenneth Dover proposes an explanation of this joke in which the gist is to be understood in terms of ‘homosexual rape as an expression of dominance’, so that Dicaeopolis is offering himself up for use as a pathic by Lamachus.Footnote ¹ Dover believes that the joke becomes ‘intelligible if the assumption is that the erastēs handles the penis of the erōmenos during anal copulation’.Footnote ² Others have seen a circumcision joke here.Footnote ³ Alan SommersteinFootnote ⁴ explains how the joke would work either of these ways:

This joke occurs in a scene in which Dicaeopolis first hails Lamachus as a hero (575) and then acts as if he is frightened by Lamachus’ gorgon-faced armour (580–2). But it quickly turns out that Dicaeopolis is really planning to use a plume from the crest on Lamachus’ helmet to make himself vomit into the shield (583–6). When Lamachus objects, Dicaeopolis suggests that the feather must come from a κομπολακύθου (‘roaring boastard’ in Henderson's translationFootnote ⁶ ). Lamachus responds by threatening Dicaeopolis, and Dicaeopolis retorts by saying that strength is not the issue (οὐ γὰρ κατ᾽ ἰσχύν ἐστιν)—and then makes the joke that is here under discussion.

Both of the options Sommerstein offers very abruptly change the tone of the way in which Dicaeopolis confronts and insults Lamachus.Footnote ⁷ Rather, the ‘shamelessness’ or ‘abject surrender’ in Dicaeopolis’ sharp interchange with Lamachus is anything but obvious. Instead, Dicaeopolis is confrontational and disdainful from the beginning, and Lamachus’ outraged response to the joke in lines 591–2 also does not seem to indicate any sudden change from aggression to (even mock) weakness in Dicaeopolis.

Another problem with the first of the interpretations Sommerstein proposes is that ἀπεψώλησας does not have to mean circumcise.Footnote ⁸ Although understanding the term to refer to circumcision is not impossible, it does require Dicaeopolis to be assuming a kind of passivity that seems not to work well with the rest of the context, or with Lamachus’ outraged response. Even if we do take the joke this way, it must be understood in a way that aligns better with the mocking tone of the entire passage. So, if circumcision really is what Aristophanes has in mind here, the joke would be roughly this: Lamachus is depicted as a big, strong man who is exceptionally well-armed. Since even a tiny blade in the hands of a relative weakling could be used to perform a circumcision, we might perhaps find comic contrast in the thought of a large sword being used instead. Or perhaps saying that Lamachus is sufficiently well-equipped to perform a circumcision could be seen as understatement to the point of insult. But perhaps we can do better than this.

Scholars have generally taken εὔοπλος to refer to Lamachus’ armament—either literally (his sword) or figuratively (his penis).Footnote ⁹ The proposed figurative reading of εὔοπλοςFootnote ¹⁰ has little to recommend it, since that reading requires a significant non sequitur: Lamachus’ supposedly impressively large phallus would hardly provide Lamachus with any significant advantage in performing the act indicated by the verb in line 592. The alternative (literal) reading, on the other hand, essentially requires us to take the whole joke to be about circumcision, and that is one way to understand these lines. But one weakness with this way of reading εὔοπλος is that it detaches the sense of this word from the εἰ δ᾽ ἰσχυρὸς εἶ in the previous line, which is not obviously an assessment of the quality of Lamachus’ armament(s). If we take the word, instead, to mean something more like ‘well prepared’ (so see LSJ s.v. ὁπλίζω), we can read εὔοπλος in a way that connects it with Lamachus’ overall strength, and thus as a general assessment of Lamachus’ capacity to perform the act in question. Accordingly, there is no need to understand εὔοπλος in a way that focusses narrowly on the quality of Lamachus’ armaments (literally or figuratively). Instead, it indicates that Lamachus is entirely ready to perform the act to which the verb refers.

Dover is perhaps right at least in proposing that we should understand the verb to refer to retracting Dicaeopolis’ foreskin.Footnote ¹¹ Accordingly, it seems best to translate the lines in question this way:

But if we understand the sense of the verb this way, then Dover's (and Sommerstein's) understanding of the joke is mistaken. According to the alternative Dover originally proposed, the joke is to be understood in such a way that Lamachus is being bidden to bugger Dicaeopolis, while also stimulating the latter's penis. Only the latter act is indicated in our text, at best. For one thing, taking the joke Dover's way requires Dicaeopolis quite suddenly to be offering to assume the role of a pathic—which would thus make him akin to all of the many people vilified in ancient comedy for having served in such a role.Footnote ¹² But there is no reason to accept this suggestion; if anything, the shoe is on the other foot.

Understood this way, the joke is, rather, that Lamachus has everything he needs to retract Dicaeopolis’ foreskin. The question we should now ask is: what does this imply? Various other jokes in Aristophanes might be adduced to support the idea that Lamachus is being invited to masturbate Dicaeopolis (so compare Ach. 1147–9, Vesp. 739–40 and 1341–4)Footnote ¹³ and thus play a role normally given to prostitutes. On the other hand, we might also imagine that the references to Lamachus’ strength and readiness are even more deflationary than this. If we imagine the joke to be even more aggressively demeaning to Lamachus, we might suppose the aim is to prepare Dicaeopolis’ penis for some further sex act—presumably, for some sexual penetration (oral or anal) of Lamachus himself, thus reducing the putatively strong Lamachus into one who is actually well prepared only to serve Dicaeopolis as a pathic recipient to the older man's lust—while also making the joke itself an even greater insult to Lamachus.Footnote ¹⁴

It is entirely possible that Aristophanes is happy enough to leave either of these options open. In either case, the insult to Lamachus is powerful and shocking—rather than acknowledging Lamachus’ proud readiness for war, Dicaeopolis reduces Lamachus to someone who is ready only to be used for sexual gratification. Such an insult is more in keeping with the rest of Dicaeopolis’ mocking of Lamachus, and also makes the best sense of the specific text at 591–2.Footnote ¹⁵