On 26 August 1346, fighting on ground of their own choosing, the English inflicted a heavy defeat on a large French army led by their king Philip VI at the Battle of Crécy.

A week later the English invested the well-fortified port of Calais, which had a strong garrison under the command of Jean de Vienne.

Edward made several unsuccessful attempts to breach the walls or to take the town by assault, either from the land or seaward sides.

[5] Although Gascony was the cause of the war, Edward was able to spare few resources for it; whenever an English army had campaigned on the continent, it had operated in northern France.

The English fleet paralleled the army's route and landing parties devastated the country for up to 5 miles (8 km) inland, taking vast amounts of loot; after their crews filled their holds, many ships deserted.

[17] They devastated the country to the suburbs of Rouen before leaving a swath of destruction, rape and slaughter along the left bank of the Seine to Poissy, 20 miles (32 km) from Paris.

They continued to devastate the land, and razed several towns, including Wissant, the normal port of disembarkation for English shipping to north-east France.

It was surrounded by extensive marshes, some of them tidal, making it difficult to find stable platforms for trebuchets and other artillery, or to mine the walls.

[33] The English settled down for a lengthy stay, establishing a thriving camp to the west, Nouville, or "New Town", with two market days each week.

Two cardinals acting as emissaries from Pope Clement VI, who had been unsuccessfully attempting to negotiate a halt to hostilities since July 1346, continued to travel between the armies, but neither king would speak to them.

On 9 September Philip announced that the army would reassemble at Compiègne on 1 October, an impossibly short interval, and then march to the relief of Calais.

[37] Among other consequences, this equivocation allowed the English forces in the south west, under the Duke of Lancaster, to launch offensives into Quercy and the Bazadais; and launch a major raid 160 miles (260 km) north through Saintonge, Aunis and Poitou, capturing numerous towns, castles and smaller fortified places and storming the rich city of Poitiers.

These offensives completely disrupted the French defences and shifted the focus of the fighting from the heart of Gascony to 60 miles (97 km) or more beyond its borders.

[38][39] Few French troops had arrived at Compiègne by 1 October and as Philip and his court waited for the numbers to swell, news of Lancaster's conquests came in.

It was believed that Lancaster was heading for Paris, and in order to block this the French changed the assembly point for any men not already committed to Compiègne to Orléans, and reinforced them with some of those already mustered.

[46] Recriminations were rife: the Marshal of France, Charles de Montmorency, was sacked; officials at all levels of the Chambre des Comptes (the French treasury) were dismissed; all financial affairs were put into the hands of a committee of three senior abbots; the King's council bent their efforts to blaming each other for the kingdom's misfortunes; Duke John fell out with his father and refused to attend court for several months; Joan of Navarre, daughter of an earlier king of France (Louis X) and previously a staunch supporter of Philip, declared neutrality, signed a private truce with Lancaster, and denied Philip access to Navarrese fortifications – Philip was considerably chagrined, but unable to counter this.

This was due to: many soldiers' terms of service expiring; a deliberate reduction by Edward for reasons of economy; an outbreak of dysentery in Neuville which caused major loss of life;[note 2] and widespread desertion.

[49] Despite his reduced numbers, between mid-November and late February Edward made several attempts to breach the walls with trebuchets or cannon, or to take the town by assault, either from the land or seaward sides; all were unsuccessful.

[52] Philip attempted to take the field with his army in late April, but the French ability to assemble in a timely fashion had not improved since the autumn and by July it had still not fully mustered.

[53] Taxes proved ever more difficult to collect, with many towns using all available funds to reinforce their walls or equip their militia, and much of the nobility crippled by debt they had accumulated paying for the previous nine years of war.

[58] In late April the English established a fortification on the end of the spit of sand to the north of Calais, which enabled them to command the entrance to the harbour and prevent any further supplies reaching the garrison.

[68] Edward also had difficulties in raising money, partly due to the unexpected timing of the need; he employed draconian measures, which were extremely unpopular.

[8] Calais was vital to England's effort against the French for the rest of the war,[30][65] it being all but impossible to land a large force other than at a friendly port.

The town had an extremely large standing garrison of 1,400 men, virtually a small army, under the overall command of the Captain of Calais, who had numerous deputies and specialist under-officers.

[30][73] Edward granted Calais numerous trade concessions or privileges and it became the main port of entry for English exports to the continent, a position which it still holds.