England is an island or, strictly speaking, part of an island, and until the development of air transport was dependent on the sea for both trade and war. The significance of seapower in the Middle Ages was the same as it was in the age of Alfred Thayer Mahan. It enabled those who possessed it to project power, carrying armies across the sea, and landing them at critical points on the enemy’s coast, choosing their own time and place.

During the series of Anglo-French wars between 1337 and 1453, which we call the Hundred Years War, English armies were able to land year after year in France, and occasionally much further afield, in the Low Countries, Castile and Portugal, with armies of up to 15,000 men, mostly mounted. By comparison, France never once succeeded in mounting a full-scale invasion of England. Invasions were planned in 1336, 1369 and 1386, but none of the armies and fleets assembled for them ever sailed. Apart from brief hit-and-run raids against the English coast, which achieved little of real strategic value, the largest forces that the French ever succeeded in taking to the British Isles were the army of some 2,000 men landed in Scotland in 1385, and about 1,800 men landed in Wales in 1403.

Both expeditions ended in disaster, mainly because of the small size of the French forces engaged, and the difficulty of supplying them across hundreds of miles of sea. The logistical challenges of invading England from France are no greater than the logistical challenges of invading France from England. So how did this striking disparity come about?

The starting point is the nature and number of the ships at the disposal of the two belligerents. The only specialised fighting ships of the Middle Ages were galleys, a form of vessel that had existed since Roman times, but which was designed for Mediterranean conditions. Galleys were deployed mainly by the Italian maritime republics, Venice, Genoa, Pisa and, later, Florence; and by the Iberian states, Aragon, Castile and Portugal. The standard model was a long, narrow, shallow-draft  vessel with a complement of 180 oarsmen and three officers. The French hired galley fleets throughout the 14th century for use against the English, initially from the Genoese, and then, from the 1370s onwards, from Castile. They also built their own oared warships at two specialised arsenals, one on the banks of the Seine outside Rouen and the other on the Mediterranean near Narbonne.

Galleys had serious disadvantages. They needed permanent teams of specialised craftsmen to build and maintain them, and experienced rowing crews to operate them. The cost was prohibitive unless they could be hired out to merchants when not required for war. The Italian maritime cities were able to do this because many Mediterranean cargoes were light and of high value: they often, for example, carried spices. Atlantic cargoes, by comparison, tended to be bulky commodities such as metals and wool, for which galleys were useless.

Galleys, moreover, had severe operational limitations in Atlantic waters. They were fast in short spurts and highly manoeuvrable. But their low freeboard made them difficult to operate in heavy seas. They also had a small carrying capacity, which meant that they could not carry more than about 30 soldiers or remain operational for more than about three weeks without having to return to port to take on fresh water. In an age when the main weapons of naval warfare were bows and arrows, grappling irons and boarding parties, the superior height of most sailing ships gave them a considerable advantage. It was not unknown for an isolated sailing ship to be overcome by galleys, but no armed sailing fleet was ever defeated by galleys in Atlantic waters. The French used oared vessels for short cross-Channel raids, but for major naval operations they used sailing ships.

Except for a brief period in the 1370s, the English depended entirely on sailing ships for their war fleets. The great majority of them were requisitioned merchantmen. The smaller ones were normally used as transports. The larger ones, with over 200 tons carrying capacity, were adapted for fighting by building timber ‘castles’ fore and aft and fortified crows’ nests at the top of the masts. These were used as platforms for archers, ‘balistae’ (essentially large crossbows mounted on timber frames) and, towards the end of our period, cannon. They are sometimes referred to in the records as ‘tower ships’. They were slow and unmanoeuvrable, which made it difficult for them to tack within 80 degrees of the wind. But unlike galleys, they had height, endurance, and a relatively large carrying capacity.

The use of requisitioned merchantmen had another advantage. It meant that there was no need for the English kings to maintain large permanent fleets or dockyard facilities. At the outset of the Hundred Years War, in 1337, Edward III owned just three ships large enough to fight at sea. By the 1350s, he had expanded his fleet, but it still comprised only 27 ships, of which only five had over 200 tons carrying capacity, the ideal size for fighting. The king’s ships were normally laid up on the strand of the Thames near the Tower of London, and later at Greenwich, where an officer known as the Clerk of the King’s Ships was responsible for their upkeep. They had permanent masters, but only skeleton crews. Seamen were recruited when required. They were hired at the quaysides or taken by press-gangs.

As for the commanders, they took advice from experienced seamen on navigation and shiphandling, but they had no specialised expertise in naval warfare. The admirals were generally noblemen whose responsibilities were primarily administrative, while the fleet commanders, also noblemen, were invariably soldiers used to fighting on land. They directed fights at sea as if they were battles on land, in formations, with bows and arrows, swords and axes. At the Battle of Sluys, England’s greatest naval victory in the Hundred Years War, the English fleet bore down on the French in three great lines abreast, in a pattern borrowed from the standard tactics of army commanders on land.

Unlike the naval strategists in the age of Nelson, Villeneuve or Jellicoe, naval commanders of the Middle Ages did not plan their campaigns around the decisive sea battle. Scouting, signalling and communication were primitive and slow, and wholly ineffective over great distances. Locating the enemy was a very haphazard affair, dependent mainly on chance encounters. The English regularly deployed squadrons of armed ships to patrol the south coast and ward off French and Castilian coastal raiders. But they hardly ever succeeded in intercepting them. The few great sea battles of the Hundred Years War generally came about as a result of attempts to break into or out of a blockaded port, when the location of the enemy fleet was known. The great fight at Sluys in 1340, the largest fleet action of the Hundred Years War, was virtually an arranged battle. The French had blockaded the great harbour of Sluys, where they knew that the English intended to land their army. There, they were successfully attacked and destroyed by the fleet of Edward III.

Much the same thing happened in 1372, when the Castilian fleet blockaded La Rochelle and wiped out the English squadron under command of the Earl of Pembroke, which they knew, or guessed, intended to land there. It happened again at Saint-Malo in 1379, when the fleet of Sir Hugh Calveley broke through the Castilian galley fleet blockading the River Rance to land an army in Brittany; and in the estuary of the Seine in 1416, when the fleet of the Duke of Bedford broke through the French and Genoese naval blockade to lift the siege of Harfleur.

The main reason for this disparity between English and French naval activity was a stark difference in the size of the two countries’ merchant marine. England’s island situation, its historic connection with Gascony, and its position as a major exporter of wool and importer of wine, both of them bulky commodities making heavy demands on shipping space, guaranteed it an important place among European ship-owning nations. At the beginning of the Hundred Years War, the English merchant fleet was probably the largest on Europe’s Atlantic seaboard. The fleet which carried Edward III to Normandy in 1346 was estimated by a contemporary at 750 ships. A comparable fleet, 737 ships, served in the 11-month siege of Calais a year later. Of these, more than 90 per cent were requisitioned merchantmen.

France’s merchant marine was much smaller. France had no major export commodity to generate investment in merchant shipping, apart from salt, which was extensively farmed in the Bay of Biscay. Moreover, for most of the 14th and 15th centuries, the French kings did not directly control the two major maritime provinces of its Atlantic seaboard, Flanders and Brittany, both of which were ruled by powerful and virtually autonomous French princes. As a result, the French government had only the ports of Picardy and Normandy and La Rochelle in Poitou to draw on for requisitioned ships. Indeed, between 1417 and 1435, when the English and their allies occupied Normandy, Picardy and Flanders, they were reduced to the single port of La Rochelle.

These facts are reflected in the surviving figures for French war fleets. In 1335, when the French king’s advisers drew up an ambitious plan to land a large army in Scotland, they reckoned to be able to find 260 ships to carry it, of which 60 would be fishing vessels suitable only for carrying stores. The general requisition of 1340, the only one for which a complete record survives, produced just 167 ships, about a quarter of the number available to England at that time.

In the course of the 14th century, however, the English progressively dissipated the great maritime advantage that they had enjoyed at the outset. The siege of Calais (1346-47) marked the apogee of English naval strength, but only 20 years later the most strenuous efforts of the admirals’ requisitioning officers failed to produce more than about a third of the fleet that had participated in the great siege. The paymasters’ records in the Public Record Office show that John of Gaunt’s army sailed to Calais in 1369 on 255 requisitioned ships, not including the king’s ships or chartered foreign hulls. Thereafter, the trend was inexorably downward. The corresponding figures were 218 in 1373, 194 in the winter of 1374-5, 188 in the summer of 1378 and 155 in the winter of 1378-9. The reality was even worse than these figures suggested, because the average carrying capacity of requisitioned ships declined during this period from about 70 to about 55 tons.

The main reason for the decline of the English merchant marine was the refusal of the English kings to pay hire for requisitioned shipping or compensation for losses in the king’s service. Judging by the few recorded transactions that we have, the average large ocean-going merchant ship represented an investment of about £500, which its owner had to recover over the relatively short lifetime of a wooden, clinker-built vessel. Persistent requisitioning destroyed the profitability of the English carrying trade and inhibited investment in new ships, provoking a catastrophic decline in the English merchant marine.

The process is graphically described in an inquisition taken in 1347 at Great Yarmouth, which at the outset of the war had been the leading shipowning port in England and much the largest contributor to Edward III’s requisitioned fleets. In 1333 its shipowners owned 90 so-called ‘great ships’ carrying between 100 and 300 tons apiece. They were requisitioned for service against the Scots or the French in every year except one between 1333 and 1347. At the end of that period, there were only 24 of them left. The rest had all been captured, wrecked, destroyed by the enemy or put out of service by wear and tear. The trading profits of the town’s shipowners had fallen so low that lost ships could not be replaced, and damaged ones were left to rot on the beaches for want of money to repair them. The town never recovered its former pre-eminence.

Over the following years, this pattern was generalised over most of England. In the autumn of 1372, the Commons complained that, 20 years before, the rivers and harbours of England had been so packed with ships that Edward III was known as the ‘King of the Seas’, whereas now England’s naval resources were so much reduced that it was no longer possible to defend the realm. The Commons put this down to persistent requisitioning for long periods every summer.

This had serious implications for the deployment of English armies in France. After 1346, English continental armies consisted entirely of mounted men, which posed special problems for their transportation. In the first decade of the war, a banneret was normally allowed shipping space for five horses, a knight for four, a squire for three and an archer for one. In addition, a man-at-arms was generally accompanied by at least one page or varlet who did not appear on the government’s payroll but needed shipping space all the same. Shortage of shipping space in the last three decades of the 14th century made it necessary to reduce the maximum allowance for a man-at arms of whatever rank to three, and some attempt was made to reduce the number of camp-followers. But the troop-carrying capacity of English ships was surprisingly small at the best of times. They had deep holds designed for bulk cargoes, and limited deck space, much of which was required by the crew to work the ship.

Men and horses are not inert bodies. Although their tolerance of discomfort was high, they could not be treated like sacks of wool. Horses had to be stowed below deck, in individual dismantlable wooden pens, while archers and men-at-arms with their pages and varlets were crammed onto open decks, wearing their armour and carrying their weapons and equipment. For the short passage to Calais or Brittany, the average English ship could carry about 30 soldiers with 15 pages or varlets and 60 horses. On longer passages, when more space was required for sleeping and for storing victuals, fodder and water, the number of troops which could be carried was smaller. In those cases where ships’ tonnages are recorded, it can be shown that one man with his page, his horse and his equipment, weighing, say, half a ton all told, required between four and six tons of cargo capacity to carry them, depending on the length of the passage.

By the second half of the 14th century, the declining number and size of English merchant ships represented a severe constraint on the scale of English operations on the continent. The ‘lift’ (i.e. the numbers that could be carried overseas in English ships in one passage) fell sharply. Edward III took an army of about 14,000 fully equipped troops to Normandy in 1346. Thirty years later, the ‘lift’ of the English merchant fleet, not counting foreign chartered vessels, had fallen to between 4,000 and 5,000 mounted men. In 1380 it was less than 2,000.

There was a particular problem about carrying armies to Gascony. Only the larger ships were suitable for the dangerous passage past the Ushant rocks and across the Bay of Biscay, and large ships were scarce. The length of the passage meant that comparable ships carried about a third fewer troops to Gascony than to Normandy or Brittany. The army of Henry of Lancaster, which arrived in Bordeaux by sea in 1345, was 2,000 strong, including 500 unmounted Welsh infantry. The army of the Black Prince, which arrived there a decade later, also by sea, was 2,200 strong, all mounted. These expeditions were less than half the size of those which were being carried across the Channel in the same period. A total of 1,600 reinforcements were sent to Gascony by sea in 1369, when the war resumed after a nine-year interval, but at least two passages were required to do it. Thereafter the English never succeeded in sending more than a few hundred men at a time to the duchy by sea.

The English occupied Calais for two centuries, between 1347 and 1558. This ought in theory to have transformed England’s strategic fortunes. Calais, in the words that an English chancery draftsman put into the mouth of Henry VI, was ‘the bolt and key to open our way to France’. With a secure base on the French coast only 20 miles from Kent, troops could be ferried across by smaller fleets, including barges and fishing smacks, operating in relays over periods as long as six weeks. In principle, there was no limit to the size of the army that could be transported. It was just a question of time.

Calais, however, lay in the extreme north of France, and in the 14th century the critical theatres of the war lay much further south, in Brittany, Lower Normandy, and Gascony. These regions were difficult to reach overland from Calais, because the great west-flowing rivers of France were formidable barriers to an army heading south.

These strategic problems came to a head in the 1370s, when the English merchant fleet reached its lowest level since the beginning of the war. In 1372, the Constable of France, Bertrand du Guesclin, overran the whole of English Aquitaine north of the Dordogne, including all of its richest provinces, with an army of just 3,000 men-at-arms and 800 crossbowmen. Although the plans of the French had been signalled for months in advance, and between 6,000 and 7,000 troops were recruited in England to counter them, it proved impossible to get these troops to France. The shipment of such a large army directly to Bordeaux was ruled out by the length of the passage and the shortage of ships of sufficient size. Instead, the Earl of Pembroke was sent by sea to La Rochelle with a small squadron of ships and chests full of coin and bullion to recruit an army locally in south-western France. The plan was for the main army to take the shorter passage to Brittany under the personal command of the king and march south to join forces with Pembroke on the Gascon march.

In the event, Pembroke’s squadron was annihilated by the Castilian fleet off La Rochelle in June and his treasure captured. The outcome of the battle was decided by the number and size of the Castilian ships and the superior seamanship of the Castilian masters and their experienced Genoese admiral, Ambrogio Boccanegra. He succeeded in trapping the English fleet against the lee shore, where they were unable to manoeuvre, pouring arrows and burning oil onto the crowded decks of their ships.

As for the English king’s army, by calling on substantially the whole English merchant fleet and supplementing it with ships and barges chartered in the Low Countries, Edward III was able to assemble a fleet of transports that the Italian trading houses reckoned at 376 vessels. Southampton or Plymouth would have been the normal ports of embarkation for a destination so far west, but because most of the ships came from east coast ports or the Low Countries, Sandwich was used instead. The fleet passed three uncomfortable weeks beating west into the prevailing south-westerly winds, while in France one stronghold after another fell to the victorious army of Bertrand du Guesclin.

Most of the English army was disembarked in Sussex at the beginning of October and paid off. Not a single ship reached France.

In the following year Edward III’s son John of Gaunt was obliged to reach Gascony overland from Calais, via Champagne and the Massif Central. It took him six months and cost him more than half his horses and much of his army.

The English drew the wrong lessons from these disasters. They decided for the only time in the Hundred Years War to acquire a fleet of war galleys. In 1371 a London-based Genoese merchant called Jacopo Provana was sent to Italy with the enormous sum of £9,500 in cash to hire a contract galley fleet from the republic of Genoa. Unfortunately, Genoa was in the middle of a civil war, and Provana’s contacts were with people who turned out to be on the losing side of it. Provana had better luck in 1373, when he returned to Italy accompanied by the poet Geoffrey Chaucer, then a squire in the royal household, who spoke some Italian. They managed to conclude an agreement in principle with the new regime in Genoa. But the project was abandoned when war broke out between Genoa and Venice in the eastern Mediterranean and the Genoese war fleet was required elsewhere. From this experience, the English government drew the conclusion that if England was to have a large fleet of oared vessels, they would have to build and man it themselves in England.

In November 1372, Edward III’s ministers persuaded Parliament to impose a tax in kind on designated towns of eastern and southern England, requiring them to build at their own expense 15 large oared barges for war service according to a standard design. These were clinker-built vessels, broader in proportion to their length than their Mediterranean prototypes and rather slower and less manoeuvrable. They also had a higher freeboard and more cargo space so that they could be used as transports for soldiers and horses or hired out to merchants when not required for war service.

We have a detailed description of one of these barges, the Paul, which was built by the Londoners. It was a large vessel, 80 feet long, with three fortified topcastles, designed to carry 60 archers in addition to its crew of 80 oarsmen. The experiment was repeated in 1377, when Parliament authorised the king to require 42 towns to construct 27 smaller barges (known as ‘balingers’) of 40 or 50 oars each. The king and a number of prominent courtiers also commissioned oared ships of their own, some of which were considerably larger. Most of the ships were built, but the experiment was not a success, mainly because the crews were not available to man them. Seamen could be conscripted by press-gangs, but that only diverted manpower from the commercial sector and reduced the availability of requisitioned tonnage. The English discovered too late that oared vessels, although comparatively cheap to build, required a great deal of maintenance if they were to remain seaworthy.

Richard II’s ministers acquired a storage yard and repair dock at Ratcliffe in Stepney, the suburban village outside London where most of the capital’s shipbuilding and repair trades were concentrated. But they could not afford to maintain a great marine arsenal such as the French had at Rouen or the Castilians at Seville. Within a few years most of the newly commissioned barges had rotted away. The king’s fleet of sailing vessels vanished at about the same time. By the time that Edward III died in 1377, his fleet had been reduced by losses and decay to four sailing ships, four barges and a galley. A year later, it was reported that only one of them, the 300-ton carrack Dieulagarde, was fit for service, and that was shortly given away to a courtier. The rest were sold off to pay the debts of the Office of the King’s Ships.

In 1380 the government finally decided to address the problem. They agreed, under pressure from the House of Commons, to pay compensation to the owners of requisitioned ships. The rate was not generous, 3s 4d per quarter per ton, and it was reduced to 2s five years later. It was too late. Ships were now so scarce that when the Earl of Buckingham was planning his campaign in France in 1380, the requisitioning officers were instructed to take ships as small as ten tons carrying capacity. Even so, they could find only 123 English merchantmen, less than a fifth of the number available 30 years earlier. Well over half of the fleet that ultimately carried Buckingham to France had been hired in Flanders and the Low Countries. There were not enough large ships to take Buckingham directly to Brittany, where he had originally intended to land. So he was obliged to go to Calais, and reach Brittany by the circuitous route round the eastern side of Paris. The result was to delay his arrival by more than three months, which contributed significantly to the failure of his campaign.

In the following year, the Earl of Cambridge encountered the same problem when he was sent with an army of 3,000 men to Portugal to mount a joint invasion of Castile with the Portuguese king. Since only the largest ships were suitable for the long passage to Lisbon and there was only a handful of them available, it was necessary for the men to sail without horses, in the hope of finding mounts in Portugal. In the event, the number and quality of horses available in Portugal turned out to be wholly inadequate. For that and other reasons, Cambridge’s mission failed as completely as Buckingham’s, but at least Buckingham returned from Brittany on English ships. The ultimate humiliation of the Earl of Cambridge came when having tried without success to invade Castile, he was dependent on the Castilian King to provide ships to take him home.

By this time, developments in France were transforming the naval balance of power. In 1381, the Duke of Brittany was reconciled to the French Crown after 40 years of intermittent rebellion. In a parallel development, in November 1382, a huge French army destroyed the army of the Flemish towns at the battle of Roosebeke, an event which began the reintegration of Flanders into the French state after more than a century of practical autonomy. Flanders and Brittany had hitherto contributed nothing to the French king’s naval resources. All of this now changed. For the first time in the Hundred Years War, the French Crown could draw on the maritime resources of the entire Atlantic coastline from the Gironde to the Hondt. The French could now contemplate an invasion of England for the first time with serious prospects of success.

The French invasion fleet of 1386 was estimated by a sound judge at more than 1,000 hulls. About 600 or 700 of these were requisitioned in France itself. The rest were chartered from Castile, Genoa, Venice, Scotland, Germany and the Low Countries. This fleet was intended to carry an army of some 6,000 to 8,000 men-at-arms with horses and 3,000 bowmen from Sluys to East Anglia, together with a mass of supplies and a complete prefabricated timber fort to protect the landing ground.

In the end, England escaped invasion more by luck than judgment, for the scale of the preparations delayed the sailing of the French armada. By the time that it was ready, the weather had turned and it was too late in the season to sail.

When, in 1415, Henry V reopened the war after a truce of three decades, he depended like his forbears on requisitioned merchant ships, supplemented by those hired by his agents on the continent. But in order to fight off the huge sailing ships of France’s Castilian and Italian allies, he needed large, well-armed fighting ships as well. Unable to find them in large enough numbers from the English merchant fleet, he began to build a specialised war fleet of his own. By the time of the Agincourt campaign of 1415, he possessed two ‘great ships’, three large captured Genoese carracks, seven smaller sailing vessels and 11 oared barges. Several more were under construction in improvised shipyards in the Solent and the Rother valley.

Henry’s fleet eventually numbered more than 30 ships. The largest of them were bigger than any commercial vessels that had yet been built in England. His first ‘great ship’, the Trinity Royal, which served as his flagship when he sailed for Harfleur in 1415, had a capacity of 450 tons. The Jesus, built at about the same time, carried 1,000 tons. But even these monsters were dwarfed by the Grace Dieu, which at 1,400 tons carrying capacity was probably the largest ship in the world in its day. It was twice the size of Henry VIII’s Mary Rose and larger than any other ship built for the Royal Navy before the 17th century. What did Henry plan to do with these ships, asked the author of the pamphlet of the 1430s, the Lybelle of Englyshe Policye? ‘It was not else’, he answered, ‘but that he caste to be Lord about enviroun of the sea.’

Nonetheless, we do not think of Henry V as the founder of the Royal Navy, and for good reason. By 1420, he had conquered the whole of Normandy and forged an alliance with the Duke of Burgundy, whose domains included Picardy, Artois and Flanders. As a result, all the major ports of northern France passed under English control. Honfleur, Harfleur, Dieppe and Calais all received English garrisons, and another English garrison at Le Crotoy guarded the mouth of the Somme. Henry had achieved his strategic object so quickly and so completely that his new fleet quickly became redundant. The English now controlled the Channel from both sides, and there was no real need for a powerful navy.

After Henry V’s death in 1422, his son’s ministers sold off his ships except for the four ‘great ships’, which were too large for commercial use. They were laid up on the mud flats of the river Hamble at Bursledon near Southampton, where they were left to rot. The Grace Dieu, the pride of Henry’s navy, had been employed on only one operation, leading the fleet that carried Henry V’s last army to France in May 1420. In 1439, the hull, by now largely rotten, was struck by lightning and burned down to the waterline.

When the Dukes of Burgundy deserted the English cause in 1435 and the English once more lost control of the Channel coast of France, they found themselves with no navy. In desperation, they turned to privateers, essentially licensed pirates who were not under the operational control of the King’s admirals, and achieved nothing of any strategic value.

‘Where ben our ships, where ben our swords become?’, asked the author of the Lybelle of Englyshe Policye. The poet lamented the passing of English seapower and set out what was to become the guiding principle of England strategy from the 16th century to the end of the Second World War:

          Cheryshe marchandyse, kepe the amyralte,

         That we bee maysteres of the narowe see.

It fell to the Tudor Kings of the 16th century to realise this ambition by creating a new navy. The navy of the Tudor kings was very different from the fleets of their medieval predecessors. With the advances of gunmaking technology, warships became floating gun platforms. This led to a revolution in warship design. To carry the immense weight of metal, they required a much broader beam, a deeper draft and multiple decks. Keels and hinged rudders made ships more manoeuvrable and enabled them to tack closer to the wind.

There was a corresponding revolution in tactics for fighting at sea. Instead of being deployed like battalions of a land army, sea battles became stand-off artillery contests, more like medieval sieges than infantry battles. The dependence on ships specially designed for fighting meant that the King now had to build his own ships and crew them with trained men. That, in turn involved the construction of an elaborate infrastructure of dockyards, stores, pay offices and so on. The age of modern naval warfare had dawned.