The Duke of Mayenne, looking to take back this key strategic port from Henry's forces and to drive him from Normandy, draws together thirty-five thousand troops, plus Cambrésis militias and Lorraine troops led by the Marquis de Pont-à-Mousson to attack the city.

Knowing that an attack against an army of this size would be pointless, and that staying in the city of Dieppe would be suicidal, Henry (after consulting with the Duke of Longueville and the Duke d'Aumont) decides to go to the city of Arques (today called "Arques-la-Bataille") and to construct such important military defenses as raising of areas and rebuilding fortifications.

Te troops of the Catholic League launch several attacks on Arques and the surrounding areas between September 15 and 29,  but royal artillery counters the forces of the Duke of Mayenne.

The attacks are extremely deadly for both sides, and soon Henry IV's side finds itself undermanned.

Henry's rescue appears from the sea on September 23, four thousand British soldiers sent by Queen Elizabeth having left England in several waves over three days.

The Duke of Mayenne, seeing these reinforcements, decides to retreat, a victory for the Royal Army.