Scorched earth
A scorched-earth policy is a military strategy that aims to destroy anything that might be useful to the enemy while it is advancing through or withdrawing from a location. Any assets that could be used by the enemy may be targeted, for example food sources, water supplies, transportation, communications, industrial resources, and even the locale's people themselves.
Battle of Blanchetaque
On 16 August, Edward burnt down Poissy and marched north. The French had carried out a scorched earth policy, carrying away all stores of food and so forcing the English to spread out over a wide area to forage, which greatly slowed them. Bands of French peasants attacked some of the smaller groups of foragers. Philip reached the River Somme a day's march ahead of Edward. He based himself at Amiens and sent large detachments to hold every bridge and ford across the Seine between Amiens and the sea. The English were now trapped in an area which had been stripped of food. The French moved out of Amiens and advanced westwards towards the English. They were now willing to give battle, knowing that they would have the advantage of being able to stand on the defensive while the English were forced to try and fight their way past them.