Somme (river) invasion fleet of William the Conqueror assembled in the Bay of the Somme, at Saint-Valery-sur-Somme. The river also featured in the 1346 withdrawal of Edward III of England's army, which forded the river at the Battle of Blanchetaque during the campaign, which culminated in the Battle of Crécy. Crossing the river also featured prominently in the campaign which led to the Battle of Agincourt in 1415. In 1636, a Spanish army led by Thomas Francis, prince of Carignan, crossed the Somme defeating a French army during the Thirty Years War threatening Paris. Most famously, the Battle of the Somme, during
Battle of Agincourt the battle was fought on a recently ploughed field, and there had recently been heavy rain leaving it very muddy, it proved very tiring to walk through in full plate armour. The French monk of St. Denis describes the French troops as "marching through the middle of the mud where they sank up to their knees. So they were already overcome with fatigue even before they advanced against the enemy". The deep, soft mud particularly favoured the English force because, once knocked to the ground, the heavily armoured French knights had a hard time getting back up to fight in