Even though the Corsairs at K-18 were less than 50 miles from the 1st Marine Division, very few were available to the Marines. Operation STRANGLE, in full swing, was not achieving the desired results. Since sightings of enemy vehicles were increasing, more and more Marine and Navy air sorties were channeled into interdiction. During 18 days of rugged fighting from 3 to 21 September, forward air controllers made 182 tactical air requests. Fighter-bombers were provided on 127 of these requests; however, in only 24 instances did the planes arrive when needed. The average delay time in getting CAS in response to requests during September was slightly less than two hours, but in 49 cases the planes were more than two hours late.[280] As a consequence, General Thomas reported, many of the 1,621 casualties suffered by the 1st Marine Division during the hard fighting in September were due to inadequate close air support. Furthermore, he said, the tactical capabilities of his battalions were strongly restricted. [280] _PacFlt Interim Rpt_ No. 3, Chap. 9, 9–14. During the planning of attacks, infantry commanders almost always desired and requested close air support. It was also desirable to have planes on station overhead should an immediate CAS need arise, for the lack of an air strike when needed could jeopardize success. However, with restricted availability of CAS planes due to participation in STRANGLE, many times desired air cover was not to be had. Attacks under those circumstances were often costly. _First Helicopter Supply Operation of History_ The relief of the three battalions of the 7th Marines by their corresponding numbers of Colonel Thomas A. Wornham’s 1st Marines took place during the night of 12–13 September. By daybreak 3/1 and 1/1 had assumed responsibility for the zones of 3/7 and 1/7, which were on their way to Division reserve at Wontong-ni at the junction of the Inje and Kansong roads. In the center, however, 2/1 could not complete the relief of 2/7. Not only was that battalion engaged most of the day with the enemy, but the units were separated--one company south of Hill 749 being unable to join the other two companies on separate spurs northwest of that height. All three were under persistent NKPA mortar and 76mm fire.[281] [281] Sources for this section are as follows: EUSAK _Cmd Rpt_, Sep 51, 35–53; X Corps _Cmd Rpt_, Sep 51, 9–12; 1stMarDiv _HD_, Sep 51, 10–16; 1st Marines _HD_, Sep 51; 1/1, 2/1, and 3/1 _HD_, Sep 51; Class “C” Rpt, _Employment of Assault Helicopters_, 1–6; Lynn Montross, _Cavalry of the Sky_ (New York, 1954), 159–162, (hereafter _Cavalry of the Sky_).