I refuse to waste brain-time thinking about this scenario, but there are a few misleading things here. In the medieval era in Europe (let's say it ends at the end of the 14th century) a vanishingly small portion of a random sample of peasants would have any military experience. It was in the early modern period that army sizes as a portion of population became significant and war became more common than peace (and even then, the exceptional states that achieved a high portion of population under arms wouldn't have ever peaked much above 4%). Little wars were fought often in the medieval era, but they generally involved smaller armies active for short periods of time, and not a whole lot of combat (just skirmishes and sieges mostly). In the early modern period, army sizes grew incredibly (in greater proportion than the increase in population) and wars in general became much deadlier.
"Standing armies" also didn't really exist in significant numbers until the 18th century. Before then they were generally very small contingents that the larger states kept around, meant mostly to just "stiffen" the main body of forces by preserving some level of training (and not much at that). Incidentally, the best way to think about armies in the early modern period (in Europe) is to imagine what you would get if militaries today were privatized by psychotic neoliberals; they weren't "professionals" and they weren't "levies", they were for the most part privately contracted regiments owned by a captain or aristocrat who paid for all expenses themselves with the expectation of regular payment from the government, with varying intentions of profit (you can imagine the sorts of things this led to).
Civil society also became more violent in the early modern period than it was in the middle ages, and the two get conflated in popular imagination. Some causes: the reformation brought with it tremendous civil strife, and popular superstitious activity like the burning of witches only became significant in the early modern period; famines brought on by a changing climate, increased taxation/rents, and the extension of the market economy led to riots; the creation for more or less the first time of a permanent underclass of homeless vagrants and the explosion in crime due to more extensive and permanent poverty in general; an increasingly draconian and violent reaction from governments to that increase in crime, and the need to preserve the hierarchical order; and a general erosion of the reciprocal social fabric that existing under feudalism.
The romantic notion of a burly hard peasant hardened by hard labor done hardly is also misleading. Long hours of manual labor doesn't translate into being super buff; if you look at most modern peasants still using unmechanized methods about as primitive, they're usually scrawny. The vast majority of a random sample of peasants would have indeed eaten less and of less variety than we do today, with little meat; generally the only peasants who ate well were the ones who were not crushed under massive rents, which were the more isolated ones that made up a smaller portion of population. Incidentally, the people who would have military experience in most periods would have also been the people who were poorest and most unfit, as in areas where there was some sort of a quota system for recruitment or even a levy, it was the people most disadvantaged in society who the rest would shift that burden onto.