the front-line had extended to in width and in depth. The Allied command ordered its air department to continue attacking all bridges on the river Vardar. At 4.00 a.m. on 17 September, Hellenic components of the 1st Division Group raided mount Preslap, a key position housing Bulgarian artillery. The Greeks rapidly descended from Golo Bilo and then began climbing the cliffs of Preslap with their bare hands. The Preslap garrison proceeded to abandon their positions and retreat eastwards. Having lost their artillery cover forces at Zborsko followed their comrades in retreat. The Timok Division conquered Topolets and advanced towards Studena Voda and Preslap while the Morava and Yugoslav Divisions overran Koutskov Kamene. At the same time, the Drina and Danube Divisions seized Gradešnica along with the Poltsista and Besistsa peaks, then halted at Melinitsa. On 18 September, the 11th French Colonial Division and the 6th Greek Regiment occupied the villages of Zovik, Staravina and , approaching towards the bridge on Crna. An Entente air raid destroyed another bridge north of Razim Bey. Bulgarian forces failed at putting a stop to the Allied offensive, abandoning their wounded and large quantities of military equipment. By the end of the day, Allied troops had advanced into enemy territory while also seizing locales of strategic importance that would later enable them to continue pushing deeper into Vardar Macedonia. Battle of Doiran On 16 September, the Allies commenced a 232 gun and 24 howitzer artillery barrage on the Bulgarian positions between Vardar and Doiran. Bulgaria responded in kind, with the artillery duel continuing during the following two days. On the night of 17–18 September, Bulgarian positions were targeted by nine salvos of gas shells, however the attack failed to produce any considerable effect due to the preceding arrival of new gas masks and the adequate training of the defenders. At 5.00 a.m. on 18 September, the British XII Corps executed a pincer maneuver on the 9th Bulgarian Division, while the Greek Serres Division and the 83rd British Brigade assaulted the Bulgarian trenches to the west, taking numerous prisoners. On the north–east direction the Crete Division and the 28th British Division advanced between the lake and Belasica, after clearing out the Bulgarian outpost line. The 26th British Division seized a number of Bulgarian security outposts but was quickly repulsed by heavy artillery fire and counter-attacks that recaptured the lost ground. It was not until 7:20 am,