Probably the best testimony on this for Henry V's campaigns specifically is Thomas Basin. Basin describes the "violences, offences and misdemeanours of the troops". The region around Caux was despoiled by "the armies of England, on the one side, and those of France, on the other". The result of which was a "dreary countryside, devoid of farmers" many of whom fled to Rouen for safety. Basin does admit that, once Henry had control of the duchy a "sort of peace."

Basin lays moral condemnation on this invasion:

"So began the English conquests in France and in Normandy: the citadel of Harfleur, which had been made famous by the exploits of its pirates, fell prey to its enemies. It is with good cause that our Lord, through the mouth of Isaiah, threatened in these terms similar destroyers, 'Woe be upon you. You who steal will you not be victims of theft yourselves. You who deceive, will you not yourselves be deceived. You who ravage, will you not also be ravaged yourselves?"

Biblical condemnation does not exactly speak to taciturn acceptance of the realities of war, but the dimension we need to consider is that Basin, as a child, and his parents, were forced to flee their home during the invasion. I don't think that it would be out of line to suggest that experience is colouring his account more than any conventional wisdom about appropriate conduct in war.

Basin is not alone in turning a sympathetic eye to the victims of the war - Enguerrand de Monstrelet makes much of the "very many mischiefs. . .done to the poor, countrymen by English, French, and Burgundians". The most remarkable passage of Monstrelet in this theme concerns a truce between the dukes of Burgundy and Bourbon, made years after Henry V's death:

"A knight of Burgundy, observing this, said aloud, 'We are very foolish to risk our bodies and souls at the will of princes and great lords, who, when they please, make up their quarrels, while we oftentimes remain poor and in distress.' This speech was noticed by many on each side for there was much truth in it, - and thus it very frequently happened."

For the Agincourt campaign specifically, Monstrelet makes special mention of the fact that the condition the inhabitants of Harfleur were reduced to was "such a piteous thing".

Following the battle of Agincourt, a large group of French prisoners was massacred, and I think that this is an illuminating case study. The killing most likely took place after the main battle was over; long enough for Henry's soldiers to let their guard down and gather up the prisoners. The killing of the prisoners was likely to have been in response to perceived resurgent threat from the French (the fear being that the prisoners would attack if they came under renewed French assault). The earliest written account, the Gesta Henrici Quinti which is, bluntly, propaganda, obscures Henry's role by making the massacre seem spontaneous rather than ordered by the king. The other major English account of the battle, Thomas Walsingham, makes absolutely no mention of it at all. In Walsingham's case it may be that he simply didn't see the killings as important enough to mention, but considering so many other accounts do, this explanation seems unlikely.

The French accounts are a jumbled mess of blame when it comes to Agincourt, and this includes the killings of the prisoners (Burgundian accounts blame an Armagnac for attempting to mount another attack, thereby provoking the massacre, for example). We'd be here all day trying to unpick it. It's the English accounts that are more illuminating. Whilst Henry doesn't come under fire for his decision in the chronicles, there is clear anxiety over the incident damaging his reputation. This is shown by the Gesta obscuring Henry's role in ordering the killing. Other accounts emphasise that the English were exhausted and that there were large numbers of prisoners. It is clear that, regardless of whether or not it was a military necessity, the slaughter of the prisoners sat uncomfortably with many of Henry's contemporaries.

On some level, ravaging the countryside was an expected part of medieval warfare, as shown by this verse, attributed to Philip, count of Flanders (1143-1191):

"Let him aid you in war, swiftly and without delay.
Destroy your foes and lay waste their country.
By fire and burning let all be set alight.
That nothing be left of them in either wood or meadow.
Of which in the morning they could have a meal.
Then with his united force let him besiege his castles.
Thus should war be begun: such is my advice.
First lay waste to the land."

Ravaging in this manner was one of the defining features of medieval warfare; nothing in Henry V's campaigns are out of step with this accepted military practice. Indeed Juvenal des Ursins attributes to Henry V the line "war without fire is like sausages without mustard". These dictums were echoed in the ever popular Vegetius.

The role of chivalric literature is worth considering. It is perhaps the coldest take one could possible have about French history to point out that the culture of chivalric literature was very strong in medieval France; Craig Taylor stated that the Hundred Years War was "a time of tremendous intellectual debate about warfare and chivalry in France". Again, Vegetius is a key text here, being pointed to again and again as a chivalric model - that practical advice about the conduct of war was thought of as chivalric literature is, in my opinion, one of the most important points to keep in mind about chivalry (though it should be kept in mind that medieval soldiers in most cases learned by doing, only reading texts like Vegetius after they had experience of war). There doesn't seem to have been much interest in England in this growing body of French literature before around 1450, so as the war was winding down. In England the preferred chivalric models seem to have remained Arthurian and biblical figures. This chivalric literature does see complaints about the destruction caused by the war, particularly from writers like Christine de Pizan. These writers debated how war should be conducted and justified. On this note it is worth pointing out that Henry V placed a great deal of emphasis on military discipline to try and prevent things getting out of control but again, sausages, mustard, etc. Another illuminating example

There was something of a sense of 'laws of war' derived from the writers of canon lawyers like John of Legnano and from the previously discussed chivalric tradition like Christine de Pizan. But in the field it's far more likely that customary practice, from the mouths of more experienced or distinguished knights and soldiers was far more important. The theorists were less concerned with the practical issues of war such as ransom, which made their utility to soldiers fairly dubious. Nigel Saul argues that the bridge between these worlds was in the form of the heralds, who would have possessed a degree of both learning and practical experience. That said, nothing in these rules prevented the kind of ravaging Henry ordered in France.

It's worth adding a quick note about Henry V's standing after Agincourt. Henry was in a marvellous position after Agincourt; his reputation amongst the princes of Europe soared. And again it's worth noting that his reputation doesn't suffer from his actions - not even the French sources attack him over the massacre of the prisoners (preferring to use it as an excuse to attack factional enemies).

To sum up, I think there was a tension at play between what was considered militarily permissible in the field, and what was seen as morally permissible by commentators. I think a good example of this is in the need to felt by English sources to justify and obfuscate Henry V's role in the massacre of the prisoners and in Monstrelet's knight of Burgundy, disgusted by the use of war as a political game. Taylor argues that in France during this period the endemic violence, caused by invasion and civil war, led to a great deal of debate about chivalry and warfare; again I think Monstrelet can be placed in this context - I have spent enough to time reading his chronicle to assert that his most admirable trait is that he never loses sight of the human suffering that these wars brought.

That said, whilst there was increasing backlash against the brutality of the Hundred Years War, none of this stopped Henry V from enjoying a glorious international reputation - whilst there's condemnation of war and violence, there's very little condemnation of Henry. Whilst many writers clearly found the treatment of con-combatants distasteful, it was, and had been for centuries, accepted military practice, with a body of literature supporting it as part of the chivalric tradition of warfare.

Sorry if this got a bit jumbled! I stopped and came back to it halfway through.