sentences:  On 29 June, following preparatory airstrikes the 1st and 4th Marine Battalions were landed by Marine helicopter squadrons HMM-164 and HMM-165 near the Wunder Beach area.By 7 July the Airborne advance had reached the southern outskirts of Quảng Trị but became bogged down as the PAVN defended tenaciously.On 11 July, following preparatory B-52 strikes, the 1st Marine Battalion was deployed by HMM-164 and HMM-165 helicopters to two landing zones 2km northeast of the city to cut Route 560, the main PAVN supply line.