second force led by Gonen himself turned south and captured Bir Lahfan and Jabal Libni. Mid-front (Abu-Ageila) Israeli division Further south, on 6 June, the Israeli 38th Armored Division under Major-General Ariel Sharon assaulted Um-Katef, a heavily fortified area defended by the Egyptian 2nd Infantry Division under Major-General Sa'adi Naguib (though Naguib was actually absent) of Soviet World War II armour, which included 90 T-34-85 tanks, 22 SU-100 tank destroyers, and about 16,000 men. The Israelis had about 14,000 men and 150 post-World War II tanks including the AMX-13, Centurions, and M50 Super Shermans (modified M-4 Sherman tanks). Two armoured brigades in the meantime, under Avraham Yoffe, slipped across the border through sandy wastes that Egypt had left undefended because they were considered impassable. Simultaneously, Sharon's tanks from the west were to engage Egyptian forces on Um-Katef ridge and block any reinforcements. Israeli infantry would clear the three trenches, while heliborne paratroopers would land behind Egyptian lines and silence their artillery. An armoured thrust would be made at al-Qusmaya to unnerve and isolate its garrison. As Sharon's division advanced into the Sinai, Egyptian forces staged successful delaying actions at Tarat Umm, Umm Tarfa, and Hill 181. An Israeli jet was downed by anti-aircraft fire, and Sharon's forces came under heavy shelling as they advanced from the north and west. The Israeli advance, which had to cope with extensive minefields, took a large number of casualties. A column of Israeli tanks managed to penetrate the northern flank of Abu Ageila, and by dusk, all units were in position. The Israelis then brought up ninety 105 mm and 155 mm artillery cannon for a preparatory barrage, while civilian buses brought reserve infantrymen under Colonel Yekutiel Adam and helicopters arrived to ferry the paratroopers. These movements were unobserved by the Egyptians, who were preoccupied with Israeli probes against their perimeter. As night fell, the Israeli assault troops lit flashlights, each battalion a different colour, to prevent friendly fire incidents. At 10:00 pm, Israeli artillery began a barrage on Um-Katef, firing some 6,000 shells in less than twenty minutes, the most concentrated artillery barrage in Israel's history. Israeli tanks assaulted the northernmost Egyptian defences and were largely successful, though an entire armoured brigade was stalled by mines, and had only one mine-clearance tank. Israeli infantrymen assaulted the triple line of trenches in the east. To the west, paratroopers commanded by Colonel Danny Matt landed