line of defense if the 3rd PS failed to intercept its force. The 21st's third flight, taking off five minutes later, headed toward Clark, although engine problems with its brand-new P-40Es reduced its numbers by two. The 17th Pursuit Squadron took off at 12:15 pm from Clark, ordered to patrol Bataan and Manila Bay, while the 34th PS at Del Carmen never received its orders to protect Clark Field and did not launch. The 20th PS, dispersed at Clark, was ready to take off but did not receive orders from group headquarters. Instead a line chief saw the incoming formation of Japanese bombers and the section commander, 1st Lt. Joseph H. Moore, ordered the scramble himself. Even though tracked by radar and with three U.S. pursuit squadrons in the air, when Japanese bombers of the 11th Kōkūkantai attacked Clark Field at 12:40 pm, they achieved tactical surprise. Two squadrons of B-17s were dispersed on the ground. Most of the P-40s of the 20th PS were preparing to taxi and were struck by the first wave of 27 Japanese twin-engine Mitsubishi G3M "Nell" bombers; only four of the 20th PS P-40Bs managed to take off as the bombs were falling. A second bomber attack (26 Mitsubishi G4M "Betty" bombers) followed closely, then escorting Zero fighters strafed the field for 30 minutes, destroying 12 of the 17 American heavy bombers present and seriously damaging three others. Two damaged B-17s were made flyable and taken to Mindanao, where one of them was destroyed in a ground collision. A near-simultaneous attack on the auxiliary field at Iba to the northwest by 54 "Betty" bombers was also successful: all but four of the 3rd Pursuit Squadron's P-40s, short on fuel and caught in their landing pattern, were destroyed in combat or by lack of fuel. Twelve P-40s from the 20th (four), 21st (two), and 3rd (six) Squadrons attacked the strafers but with little success, losing at least four of their own. The Far East Air Force lost half its planes in the 45-minute attack, and was all but destroyed over the next few days, including a number of the surviving B-17s lost to takeoff crashes of other planes. The 24th Pursuit Group flew its last interception on December 10, losing 11 of the 40 or so P-40s it sent up, and the surviving P-35s of the 34th PS were destroyed on the ground at Del