The army being thus posted, a trumpeter was sent, on the 9th of August, to summon the garrison to surrender. General Boileau answered, that he intended to make a vigorous defence of the town with which his Majesty had intrusted him. In the meantime, William had ordered up his train of artillery from Dublin. They were on their way to join him, when a spy from William's camp went over to the enemy, and informed them of the route, the motions, and the strength of the convoy. Sarsfield at once set out with a strong body of horse. He passed the Shannon in the night, nine miles above Limerick, lurked all day in the mountains near Ballyneety, and waited for the approach of the convoy. The men of William's artillery, seeing no enemy, turned out their horses to graze, and went to sleep in the full sense of security. Sarsfield's body of horse came down upon them, slew or dispersed the convoy, and took possession of the cannon. Sarsfield could not, however, take the prizes into Limerick. He therefore endeavoured to destroy them. Cramming the guns with powder up to their muzzles, and burying their mouths deep in the earth, then piling the stores, waggons, carriages, and baggage over them, he laid a train and fired it, just as Sir John Lanier, with a body of cavalry, was arriving to rescue the convoy. The explosion was tremendous, and was heard at the camp of William, more than seven miles off. Sarsfield's troops returned to Limerick in triumph. Notwithstanding these grievous discouragements, William resolved to persevere. He recovered two of the guns, which remained uninjured. He obtained others from Waterford. The trenches were opened on the 17th of August. A battery was raised below the fort to the right of the trenches. Firing went on on both sides. Several redoubts were taken. By the 25th, the trenches were advanced to within thirty paces of the ditch near St. John's Gate, and a breach was made in the walls about twelve yards wide. The assault was ordered to take place on the 27th. The English grenadiers took the lead, supported by a hundred French officers and volunteers. The enemy were dislodged from the covered way and the two forts which guarded the breach on each side. The assailants entered the breach, but they were not sufficiently supported. The Irish rallied. They returned to the charge, helped by the women, who pelted the besiegers with stones, broken bottles, and such other missiles as came readily to hand. A Brandenburg regiment having assailed and taken the Black Battery, it was blown up by an explosion, which killed many of the men. In fine, the assault was vigorously repulsed; and William's troops retreated to the main body, with a loss of six hundred men killed on the spot and as many mortally wounded.