They reached Brittany on 26 October after a storm-wracked three-week passage and Edward advanced on the major Breton town of Vannes.

The naval component went ahead, was mauled by a force of mercenary galleys and then failed in an attempt to take Vannes by a coup de main.

English raiding parties devastated large parts of eastern Brittany, but attempts to reinforce or supply Edward from England failed.

Philip now found the idea of having a relative as the duke attractive, as it would bring the traditionally semi-autonomous province more firmly under royal control; he therefore despatched an army to support Charles.

From there Joanna retained control of most of western Brittany, setting up her son as the faction's figurehead and heir to his father's claim to the duchy.

She despatched her senior counsellor, Amaury of Clisson, to Edward III of England, with a large sum in cash, to encourage rapid English military intervention.

[22] Strategically Edward had the opportunity to set up a ruler in Brittany at least partially under his control, which would provide access to Breton ports, greatly aiding England's naval war and giving ready entry to France for English armies.

[note 2] The Admiral of the North Robert Morley applied draconian measures to impress and retain ships; however, they took time to have effect.

William of Northampton was supposed to sail from Portsmouth on 8 July 1342 in command of the first contingent of the English army, 1,350 men, but on that date not a single requisitioned ship was present.

Morley's heavy-handed policy of threats and confiscations eventually bore fruit, and 440 ships were assembled, split between several ports with the largest group in the Solent.

Even this fleet would have to make several trips if it were to carry the total of 6,000 men Edward wished to deploy to Brittany, and contrary winds caused the departure of the first English echelon to be repeatedly put back.

He despatched two cardinals to attempt a permanent settlement of the Anglo-French war; they were well received by Philip in June, but Edward would not even allow them to cross the Channel.

By July Joanna had been forced back to the far west of Brittany and was besieged in the port of Brest, the only remaining fortified place still held by her faction.

This force marched 30 miles (50 km) from Brest to Morlaix, a port on the north coast of Brittany with strong fortifications and a secure harbour, and laid siege to it.

Charles became aware his force greatly outnumbered the English, despite the detachments to Picardy, and took his army west in an attempt to relieve Morlaix.

[39][note 4] The 260 English ships which had disembarked Northampton's expedition at Brest on 18 August, together with those which had landed Robert of Artois's reinforcements were supposed to immediately sail back to England.

The rest of the council abandoned attempts to cross the Channel in winter and agreed to reassemble with an army of 6,000 – the large majority much-needed infantry – on the unrealistically early date of 1 March.

[52][note 5] The siege did not require the entire army and large detachments were sent on chevauchees across eastern Brittany to devastate the region and capture the fortified places.

One expedition, commanded by the Earl of Salisbury, razed the outskirts of Dinan and devastated the area around Dol, 100 miles (160 km) north of Vannes.

However, there were fewer than 5,000 English troops in Brittany, and the term of service of many was running out; it is known that 400 Welsh archers left the army on 17 December for this reason.

[50] No food supplies were arriving for Edward by sea, and although he sent out columns over a broad area, foraging in winter yielded thin returns.

[54][49] The French were perturbed by Edward's landing in Brittany, when he was expected to invade further east, and by his taking the field so late in the season, when their armies had been disbanded.

The army was based at the main French supply centre of Angers[55] with King Philip's oldest son, the Dauphin John, Duke of Normandy, in command.

They had been observing events from Avranches, just over the Breton border, and were allowed no closer than Malestroit, 18 miles (29 km) from the main English camp.

[61] Vannes was to be held by the Pope for the duration of the truce, Philip was to immediately free John of Montfort[56][57] and there was a general exchange of prisoners.

[64][65] Edward left for England, enduring another winter storm which scattered the fleet and sank several ships, and arrived on 1 March.

He was mistaken, and the Breton Civil War ground on as a disjointed and inconclusive series of petty sieges, skirmishes and truces,[67][68] with the English and their Montfortist allies holding almost the whole of Brittany by 1345.

[69] Late in 1343 Montfortists in Vannes rose against the Pope's authority, expelled his garrison and delivered the town to the English, who held it until the end of the Breton Civil War in 1364.