As the main point of attack, Vauban chose the Front of the plain (New Gate front). Furthermore, an additional point of attack and several feint attacks were planned. From early May, the actual siege trenches were dug. With the help of sap trenches, Vauban approached the fortress in two locations. The closest Front was still half a gunshot away from the covered passages of the city. Both points of attack were linked through a connecting trench. The French set up four batteries for the siege artillery, which were aimed at the main point of attack. Along with normal guns, mortars were used. In the night of 8 May, the cannons started firing on the city. The defenders reacted on 9 May with several sorties and destroyed several offensive buildings, but could not stop the construction work. On 11 May the besiegers were within 30 steps of the closest covered passage of the fortress. Three parallels connected the trenches. Additional gun batteries were brought in. At other locations, the trenches were also nearing the city.