In the second half of the 14th century Edward II supported Jean de Monfort, Comte de Bretagne, in the fight against Charles de Blois who sought to gain the power over the duchy of. On the side of Jean de Montford many English soldiers were fighting against Charles de Bloi. The battle of Lanmeur took place in 1341 near the town of Morlaix.

Driven back from the Siege of Morlaix by Charles de Blois, an English army of about 3,000 men including about 1000 knights and 2000 bows and others under the earls of Northampton, Derby and Oxford was forced late in the day to give battle between Morlaix and Lanmeur.

The French force was considerably superior in numbers, possibly 15,000 (other sources say 12,000) strong including probably 3,000 men-at-arms and 1,500 Genoese crossbow men, the balance being local levies. The English drew up astride the Morlaix-Lameur road, on a ridge with a wood to their back, digging camouflaged pits just within bowshot.

The French attacked in column in 3 well spaced battles with Galleti (Breton infantry) and the Genoese crossbow men to the fore. The crossbow men and the Breton infantry were not able to stand against the clouds of arrows pouring down on them and broke.

The first French cavalry battle then advanced, charging headlong into the concealed pits. Many of the English broke ranks at this, only to be caught in the open by the advance of the third French battle and driven back on the wood.

Eventually, unable to penetrate the stiffly defended wood, the French withdrew, the two forces disengaging. The battle had a relatively short duration of only some hours. The end result was a victory for the Anglo-Breton army.