Being shallow-draught vessels propelled by banks of oars the galleys could penetrate shallow harbours and were highly manoeuvrable, making them effective for raiding and ship-to-ship combat in meeting engagements.

The French were able to disrupt English commercial shipping, principally the Gascon wine and the Flanders wool trades, as well as raiding the south and east coasts of England at will.

Operating the galleys was a specialist activity and called for highly trained crews, who were normally also drawn from Genoa, Monaco and, to a lesser extent, other Mediterranean ports.

[11] Cogs had a deep draught, a round hull and were propelled by a single large sail set on a mast amidships.

They were converted into warships by the addition of wooden "castles" at the bow and stern and the erection of crow's nest platforms at the masthead.

Their high freeboard made them superior to the oared vessels in close combat, particularly when they were fitted with castles from which arrows or bolts could be fired or stones dropped on to enemy craft alongside.

By English common law, the crown was required to compensate the owners of ships impressed into service, but in practice, the king paid little and late, which caused shipowners to be reluctant to answer summonses to arms.

[15] In January 1340 the English successfully raided the port of Boulogne, where the majority of the French galley fleet was drawn up on the harbour beach and was inadequately guarded.

Taking advantage of mist, the English surprised the French and destroyed 18 galleys, 24 other ships, large stocks of naval equipment and much of the harbour district before being driven off.

[19][20][21] Although Gascony was the cause of the war, Edward was able to spare few resources for it, and determined to campaign with his main force in north-eastern France in 1340.

He wished to land his army and link up with his continental allies: several states of the Holy Roman Empire; and the Flemings, who had revolted against France during the winter and launched an April offensive, which had failed.

A French offensive against these forces commenced on 18 May, meeting with mixed fortunes; Edward's outnumbered allies were desperate for the English army to reinforce them.

[26] For the most part they lack detail, so much so that the historian Kelly DeVries has commentated that for some aspects of the battle "we have only a patchwork of interesting anecdotes to lead us to any conclusions.

[28][note 1] Edward had planned to ship his army to Sluys (modern Sluis), in Flemish Zeeland, in mid-April, but most English merchantmen, aware they were unlikely to receive the payments they were entitled to, were refusing to muster.

On 10 June the council received with consternation news that the Great Army of the Sea had arrived at Sluys, the main port of Flanders, on the 8th.

A senior adviser, John de Stratford, Archbishop of Canterbury, insisted that putting to sea would risk the loss of the King and the whole expedition should be cancelled.

Meanwhile, the horses which had already been loaded were unloaded and the erstwhile transports were rapidly converted to warships by having forecastles, aftercastles and crow's nests added.

In a feat which the modern historian Jonathan Sumption describes as "truly remarkable" a sizeable fleet had been assembled at the Orwell by 20 June.

Edward anchored at Blankenberge and in the evening sent ashore Reginald Cobham, Sir John Chandos and Stephen Lambkin to reconnoitre the French fleet.

Barbavera, the experienced commander of the galleys, was concerned about this, realising they would lack manoeuvrability in their anchorage and be open to attack from the ship-based English archers.

He viewed Barbavera as a mere commoner and near pirate, and wishing to take no chances of the English slipping past, insisted on holding a position blocking the inlet.

[40][note 2] After nearly a day linked by chains and ropes, and with wind and rain working against them, the French ships had been driven to the east of their starting positions and become entangled with each other.

Béhuchet and Quiéret ordered the ships to be separated, although in the event this proved difficult, and the fleet attempted to move back to the west, against the wind and the tide.

[19][43][44][45] The modern historians Jonathan Sumption and Robert Hardy separately state that the English archers, with their longbows, had a rate of fire two or three times greater than the French crossbowmen and significantly outranged them:[46] Hardy reckons the longbows had an effective range of 300 yards (270 metres) compared with 200 yards (180 metres) for the crossbows.

The two French commanders were both captured and Béhuchet was hanged from the mast of his own ship, while Quiéret was beheaded, in vengeance for the massacre they had overseen at Arnemuiden two years earlier and for their raids on the English coast.

[59] Tactically the battle allowed Edward to land his army, which went on to besiege Tournai, a city in Flanders loyal to Philip VI,[60] although the campaign ended in failure.

Within a month a French squadron under their new admiral, Robert de Houdetot, captured 30 merchantmen from an English wool convoy and threw the crews overboard.

[61] French ships continued to capture English merchantmen in the North Sea and to run men and munitions to their allies, the Scots.

Nevertheless, the naval historian Graham Cushway says the loss of mariners economically devastated Norman and Picard maritime trade.

The inscription reads: IHC TRANSIENS PER MEDIUM ILLORUM IBAT ("Jesus passing through the midst of them went his way"),[66] an antiphon based on the Gospel of Luke 4:30, a text which was commonly invoked at the time for protection against harm in battle.