In 1915 trench warfare commenced with both sides developing impregnable defences; leading to high casualties in return for minimal gains. At the Battle of Festubert (9–16 May) – which was launched in support of the French attack south of Vimy Ridge and included the first British night action of the war – the 2nd Ox and Bucks were part of the second wave of the 5th Brigade attack and, during the course of the battle, suffered just under 400 casualties: the largest number the regiment had sustained in a single battle since the Siege of Badajoz over 100 years earlier. The 2nd Ox and Bucks were involved in heavy fighting at Richebourg l'Avoue on 15–16 May. The 2nd Ox and Bucks and other battalions of the regiment also saw action at the Battle of Loos (25 September – 8 October): 2nd Ox and Bucks took part in the subsidiary attack at Givenchy with 263 casualties on 25 September. The Ox and Bucks 5th (Service) Battalion went into the Battle of Loos on 25 September 1915 at a strength of 17 officers and 767 men and only two officers and 180 men survived the battle. The 2nd Battalion took part in the subsequent attack against the Hohenzollern Redoubt (13–19 October). Following the battle of Loos few pre-1914 2nd Ox and Bucks officers remained, they had either become casualties or promoted to take up positions in other battalions. The gallantry awards made to members of the battalion for bravery during the battle of Loos included the award of the Distinguished Conduct Medals to CSM Fred Clare and to Acting Corporal Horace Duester.