Between 9–14 January, MAG-33 participated in a USAF-USMC joint operation to strike the rail system at Sinanju, 45 miles north of the enemy capital, and at Yongmi-dong, to the northwest across both the Chongchon and Taedong Rivers. During the six-day Operation PARALYSIS, Marine and Air Force jet squadrons flew flak suppression and interdiction missions, knocking out ground-based air defense weapons and damaging and destroying bridges, rails, and rolling stock. At night FEAF Bomber Command, with Flying Nightmare escorts, worked over the communications net, including repair facilities; during daylight, the fighter-bombers attacked marshalling yards near Sinanju, where railroad cars were stacked up awaiting repair of the river bridges. Bomb assessments and intelligence reports showed that two major rail lines were inoperative for 16 days and that, as General Barcus had predicted, the Chinese “hurriedly increased their antiaircraft defenses in the Chongchon estuary and shot down seven fighter-bombers.”[326] [326] Futrell, _USAF, Korea_, p. 582. Following this operation, Colonel Robertshaw’s jets from VMFs-115 and -311 achieved extremely effective close air support in strikes flown 24 January in the I Corps area. About a month later, with an F9F as an airborne command post and with Lieutenant Colonel Walt Bartosh on his wing, the MAG-33 commander directed the operations of 208 USAF and Marine aircraft on another mass strike. The two-day mission was flown on 18–19 February against the North Korean tank and infantry school southwest of Pyongyang. More than 240 buildings were destroyed in 379 sorties. The attack was one of the largest all-jet fighter-bomber strikes of the war. Colonel Robertshaw thereby became the first Marine to lead such a large joint air-strike force from a CP aloft. And the next month, on 8 March, the Group CO flew the first Marine jet night MPQ mission, dropping six 250-pound bombs from an F9F-2 Panther on an enemy ammunition dump. _Behind the Lines_[327] [327] Unless otherwise noted, the material in this section is derived from: _PacFlt EvalRpts_ No. 5, Chaps. 8, 9, No. 6, Chaps. 9, 10; 1stMarDiv ComdDs. Jan-Feb 53; 1/1 ComdD, Feb 53; HMR-161 ComdD, Feb 53; Montross, _SkyCav_.