We are familiar with how much the Romans loved their wine. The visitor to Pompeii, the southern Italian city which in 79 AD was preserved in remarkable condition underneath a layer of volcanic ash emitted by the eruption of Mount Vesuvius, will see many frescoes and murals in the houses of wealthy Romans there which showed Romans drinking wine and socializing.
It was intrinsic to Roman society. But few are aware of the fact that there was another Roman wine beverage that was drunk in huge quantities across the Mediterranean world in Roman times. This was posca.
What was Posca?
So what was posca? Posca was a beverage made in Roman times from wine that had begun to turn vinegary. It was diluted down with water and infused with herbs such as thyme, anise, fennel, and cumin to cut through the acidity. As with so much else in Roman cultural and dietary habits, the practice of drinking posca originated amongst the Greeks and the name for it may derive from the Greek language, meaning ‘very sharp’. Alternatively, posca may come from Latin, meaning ‘to drink’, though the Greek etymology is more likely.
The Consumption of Posca
There are many literary references to posca from both the republican and imperial periods which attest to how widespread consumption of it was across many centuries of Roman history. For instance, the Roman comedic playwright Plautus refers to the beverage in his plays. He was writing in the early second century BC when Rome was still just emerging as the dominant power of the Western Mediterranean. Three hundred years later the encyclopaedist Pliny the Elder testified to the extensive use of posca in his Natural History.
Inevitably, given that this was a makeshift beverage designed to use up bad wine, posca was primarily drunk by the poorer classes of Roman society. It was especially popular amongst the rank-and-file soldiers of the Roman legions and eventually became part of their official rations. A codex dating to 360 AD indicates that Roman legionaries were given wine and posca on alternating days, presumably to save the imperial exchequer money at a time when the Roman Empire had become incredibly militarized and over 50% of the imperial budget was spent on the military.
Posca and Jesus
Whether we realize it or not, we have all actually heard of posca before. Though the name of it is not generally provided in popular accounts of the crucifixion and death of Jesus Christ, it was posca, not wine or vinegar, which was offered to the Christian messiah as he lay dying on the cross according to the Gospel of Matthew. In this the Roman wine beverage was provided to Jesus by some Roman soldiers who soaked a sponge in the liquid and then raised it up to Jesus’s lips. This would certainly seem to chime with the strong links between posca and the Roman legionaries. 
The Afterlife of a Roman Beverage
The consumption of posca certainly did not die out with the fall of the Western Roman Empire in the fifth century AD. Consumption of it, particularly within the military, continued in the Eastern Roman Empire or Byzantine Empire for centuries thereafter and we find mention of posca in Byzantine sources such as the writings of Paul of Aegina as late as the seventh century. It appears to have developed a new life as a medicinal tonic at this time. Clearly, though, later generations were not convinced and the use of posca disappeared by the advent of the High Middle Ages. 
Emperor Hadrian and Posca
Undoubtedly posca was a drink of the poor in Roman times. But many generals and wealthy individuals were affected to drink it in order to show solidarity with the Roman legionaries, the rank-and-file soldiers of the Roman war machine. None was as senior as Emperor Hadrian, who ruled Rome between 117 AD and 138 AD as one of the so-called Five Good Emperors of the Pax Romana of the second century AD.
Hadrian conducted a tour of all of the Roman provinces to reform various military, administrative and social matters, one which lasted years and resulted in his spending time in the camps and forts of many Roman legions. During the course of this, he would often drink posca, as noted in the Historia Augusta, a collection of biographies of the Roman emperors written in the fourth century. Thus, far from being limited to the poor of Roman society, posca was often consumed by even the most wealthy and powerful. 
10 July 138 – On in this day in 138 AD Emperor Hadrian died in the town of Baiae in southern Italy overlooking the Bay of Naples. He was 62 years old and had ruled for 21 years in one of the most successful reigns in Roman imperial history. Hadrian’s reign was characterized by an extended tour of all of the Roman provinces which he undertook over many years in order to reform various military, administrative and social matters. This resulted in him spending considerable amounts of time in the camps and forts of many Roman legions.
 William Chester Jordan, ‘The Last Tormentor of Christ: An Image of the Jew in Ancient and Medieval Exegesis, Art and Drama’, in The Jewish Quarterly Review, New Series, Vol. 78, Nos 1–2 (July – October, 1987), pp. 21–47; ‘Posca’, in Andrew Dalby, Food in the Ancient World From A To Z (London, 2013), p. 270; http://pass-the-garum.blogspot.com/2013/09/posca.html [accessed 1/10/22].
 Andrew Dalby, Tastes of Byzantium: The Cuisine of a Legendary Empire (London, 2010), pp. 90–91.
 Anthony Everitt, Hadrian and the Triumph of Rome (London, 2009); Danny Danzinger and Nicholas Purcell, Hadrian’s Empire: When Rome Ruled the World (London, 2006); ‘Posca’, in Andrew Dalby, Food in the Ancient World From A To Z (London, 2013), p. 270.