Chauvel arrived on 12 May 1915 and took over the critical sector, which included Pope's Hill and Quinn's, Courtney's and Steele's Posts, from Colonel John Monash. Open to Turkish observation on two sides, these four advanced posts at the top of Monash Valley were the linchpin of the defence. Chauvel reorganised the defence, appointing permanent commanders for the posts. He also formed special sniper groups who eventually managed to suppress the Turkish snipers, making it safe even for mule trains to move up Monash Valley. Chauvel's brigade soon found itself under heavy pressure from the Turks. On 29 May 1915, the Turks fired a mine under Quinn's Post and broke into it. The permanent commander of the post, Lieutenant Colonel J. H. Cannan was absent on leave and the acting commander, Lieutenant Colonel G. J. Burnage was wounded in the fighting. Chauvel responded by bringing up reserves and appointing a temporary post commander, Lieutenant Colonel H. Pope, with orders to drive the Turks out at all costs. Major S. C. E. Herring was miraculously able to charge across the open practically unscathed, his attack having coincided with a Turkish one on another part of the post so that the Turkish machine gunners could not shoot without hitting their own men. There were in fact only about seventeen Turks in the post, who eventually surrendered. Chauvel's decision may have been the wrong one, but it was decisive; he was also lucky. For this action, he was mentioned in despatches.