What stopped France from ever invading England?

by Sitchaux

William the Conqueror royally screwed over the Feudal balance in England and, from what I understand, the Hundred Years War can trace itself back to it. But how could a King of England ever pull in as much manpower as France, being about four times the size of England. What would stop a French invasion? Great Britain could probably face them off, but before GB formed, I can't find what protected England in a war with France.

Thanks in advance

duckofyork

Hiya! Couple of important things to go through here, so bear with me:

First, it is a very bad idea to overlay a modern map of France over the medieval kingdom and try to do analysis based off of it. Yes, they cover roughly the same territory, but the context is completely different. To start with the French Kings in the High Middle Ages directly administered a very small portion of their kingdom, a region called Ile-de-France, which encompasses Paris, Orleans, and some land in between. France had a very weak monarchy, many of the great peers were largely autonomous (they had their own regional courts, taxation bureaucracy, and occasionally their own currencies) and controlled far more wealth and land than the king himself. The relation between these regions and the Kingdom of France was often times merely the oaths of homage and fealty between the vassal lord and the king. Because of this context, France tended to have far more regionalism than England, where apart from Wales and the unique privileges of the marcher lords, the nobility coalesced and fought towards the center. French nobles could strive for their own autonomy and/or seek to overwhelm the king himself. Many of the stronger Kings of the medieval era sought to increase their own territory through inheritance, confiscation, vassalage, and conquest, but you can see that their focus would be trying to gain greater control of the kingdom they already had rather than trying to conquer another one. This situation left the French kings in a very vulnerable position, particularly in the mid-to-late 1100s, when a single vassal held more than half of the French Kingdom as Duke of Aquitane, Duke of Normandy, Count of Poitiers, and Count of Anjou. This vassal also happened to the King of England :)

I bring this up for two reasons. First, I want to emphasize that the King of France would not be able to effectively mobilize all the resources of "France." These kings would often try to gain more control of their kingdom, directly control more land, better obligate their vassals. Secondly, this gives some context for the King of England waging war across the channel. They have resources available to them within France, particularly the duchy of Aquitane, which was their longest-held continental possession. But with these resources also comes an interest in the affairs of France, since a stronger French king is going to eventually want to gain more control of the territories held by his vassals.

So my last point is this, if you are looking for occasions when the "Kingdom of France" tried to invade the "Kingdom of England," you will be left with few results. England had vested interests in France as well as friendly territory to base campaigns from. However, this doesn't mean that someone from France with an interest in England would not mount an invasion or campaign against England, often with the backing and support of the French King. So to go off the top of my head:

*The Norman Conquest

*The Anarchy - Empress Matilda and the future Henry II of England mounted their campaigns from Normandy, landing in southwest England which was their base of support

*The Barons' War - the English Nobility, with close ties and landholdings across the channel, invite the heir to France, Prince Louis the Lion to be King instead of King John. Louis arrived and occupied most of southeastern England with support from the local nobility and was formally acclaimed as King of England at St. Paul's Cathedral with much of the city and nobility (including King Alexander of Scotland) present. He was eventually repulsed when John died and William Marshal convinced the nobility to back the minor Henry III

*Invasion of Queen Isabella and Roger Mortimer - in response to the unpopular rule of King Edward II, his wife Isabella of France and the exiled Roger Mortimer, Earl of March, assembled mercenaries in France and invaded England. They successfully deposed Edward II and ruled in the name of Isabella's son, Edward III.

*Hundred Years' War - After the English losses towards the end of the reign of Edward III, the French began raiding the English coast, and thought about building up an military force to attack England proper. However, the death of Charles V and the infighting during the regency of Charles VI prevented this from coming anywhere near fruition.

*The mess that was the War of the Roses. In a period of about 20 years, a powerful noble, the Earl of Warwick fell out with Edward IV, rebelled, fled to France, made an alliance with the deposed family of Henry VI, invaded in his name with support from the French King and deposed Edward IV. Edward IV fled to Burgundy (which France argued was its vassal) won the support of the Duke of Burgundy, invaded England, deposed and killed Warwick, Henry VI, and Henry VI's son. After Edward IV dies, Henry Tudor takes up the Lancastrian mantle, assembles various mercenaries and exiles in France and Brittany (again, France claimed Brittany as a vassal), landed in Wales, killed Richard III at Bosworth and became King.

*The Jacobite Pretenders - well outside the medieval period, but almost entirely backed by the Bourbon Kings of France.

So I guess my point here is that people did invade England from France if they had the interest and support on both sides of the channel to do so. Just because the King of France never mounted an invasion of England doesn't mean that it wasn't possible or attempted. Please let me know if this helps or if you have follow-ups/want further reading.

Lainncli

Others may be able to expand upon this, but I believe an essential factor that prevented French invasions were simply logistics. English kings retained territories in France throughout almost the entirety of the Hundred Years War, allowing a "base" from which English armies could push into the heart of France. In contrast, the French often attempted to secure such a beachhead by allying with anti-English forces in Wales, Scotland and Ireland. In these cases, a mixture of weak allies, transport problems and (later) English naval superiority often scuppered French plans.

Furthermore, for many wars in the medieval period, the primary measure of French success was in re-taking lands in France and continental expansion - The invasion of England was not seen as necessary and they never asserted any claim to the English throne, which obviously was not the case vice-versa. French monarchs may also have been wary to committing to overseas wars due to the presence of strong neighbours in Spain, Burgundy and Germany whereas only Scotland (infrequently) ever proved any threat to English dominance of the isles.