The August Offensive or 'Anzac Breakout' at Gallipoli was an attempt to break the stalemate of the campaign. It saw some of the bloodiest fighting since the landing as Commonwealth and Turkish troops fought desperate battles at Lone Pine, German Officers' Trench, Turkish Quinn's, The Chessboard, The Nek, The Farm, Hill Q, Chunuk Bair, and Hill 971. The offensive was designed to allow the allied forces to 'break out' of the Anzac beachhead below the Sari Bair Range.
The capture of Chunuk Bair by the New Zealanders resulted in some of the bloodiest fighting at Gallipoli and was key to the entire August offensive. While it was taken and held for a few days - it's recapture by the Turks on 10 August 1915 decided the fate of the Gallipoli Campaign. Within four months the Allies were forced to evacuate the peninsula, leaving it to the Turks - a decisive victory for the Ottoman Empire
Death on Bloody Ridge: Chunuk Bair - the battle that decided the fate of the Gallipoli Campaign, focuses solely on this one decisive battle.