The Turks blockaded the harbour and bombarded the town with field artillery from the land side, followed by almost daily infantry attacks. They also sought to undermine the fortifications through tunnels and mines. The artillery fire was slow in inflicting serious damage to the massive walls, but after five weeks, on 4 September, two large gunpowder mines exploded under the bastion of England, causing a 12-yard (11 m) portion of the wall to fall into the moat. The attackers immediately assaulted this breach and soon gained control of it, but a counterattack by the English brothers under Fra' Nicholas Hussey and Grand Master Villiers de L'Isle-Adam succeeded in driving them back. Twice more the Turks assaulted the breach that day, but the English and German brothers held the gap.