Siege of Khartoum stores dwindled and starvation began to set in for both the garrison and the civilian population. Communication was kept through couriers while Gordon also kept in contact with the Mahdi, who rejected his offers of peace and to lift the siege. On 16 September an expedition sent from Khartoum to Sennar was defeated by the Mahdists, which resulted in the death of over 800 garrison troops at Al Aylafuh. By the end of the month, the Mahdi moved the bulk of his army to Khartoum, more than doubling the number already besieging it. As of 10 September 1884, the civilian
HMS Khartoum (F45) and the sloop in search for "Torricelli" near Perim Island. After interception, "Khartoum" and these warships took part in a surface engagement with the submarine, during which "Torricelli" was sunk and "Shoreham" damaged. However, during the battle, "Khartoum" was hit by return fire which damaged the after torpedo tube mounting. Some five and a half hours later, at 11.50am (local time), a torpedo's compressed air chamber exploded, propelling the warhead through the deck house of number 3 4.7-inch mount. and causing a serious uncontrollable fire from a ruptured oil tank there. This resulted in an explosion of the ship's artillery