All of the Croatian defences were away from the Old Town, except for Fort Imperial about to the north. The fortress was attacked at 5:50 amminutes after the bombardment of the Old Town began. The attack was executed by the 3rd Battalion of the JNA 472nd Motorized Brigade, advancing simultaneously from two directions. The primary attack consisted of a company-sized force, and the secondary of a platoon of infantrymenboth supported by T-55 tanks and artillery. By 8 am, the infantry reached Fort Imperial, forcing the defending force to retreat into the fortification and request help. Marinović ordered HV artillery to fire directly onto the fortress and dispatched a special police unit to reinforce the Fort Imperial garrison. By 2 pm, the JNA called off the attack. That day, "Sveti Vlaho"—the first vessel commissioned by the Armed Boats Squadron Dubrovnik and named after the patron saint of the city Saint Blaise—was sunk by a wire-guided missile.