underwent training in England after its transfer from Australia. In July 1916, the AIF commenced operations with the Battle of the Somme, and more specifically with the Attack at Fromelles. Soon after, the 1st, 2nd and 4th Divisions became tied down in actions at the Battle of Pozières and Mouquet Farm. In around six weeks, the operations caused 28,000 Australian casualties. Due to these losses and pressure from the United Kingdom to maintain the AIF's manpower, Prime Minister Billy Hughes introduced the first conscription plebiscite. It was defeated by a narrow margin and created a bitter divide on the issue of conscription throughout the 20th century. Following the German withdrawal to the Hindenburg Line in March 1917, which was better defended and eased manpower restraints, the first Australian assault on the Hindenburg Line occurred on 11 April 1917 with the First Battle of Bullecourt. On 20 September, the Australian contingent joined the Third Battle of Ypres with the Battle of Menin Road, and continued on to fight in the Battle of Polygon Wood, which lasted until 3 October; in total, these tow operations cost roughly 11,000 in Australian casualties. Until 15 November 1917, multiple attacks at the Battle of Broodseinde Ridge and the Battle of Passchendaele occurred, but, failed to take their objectives following the start of the rain and subsequent muddying of the fields. On 21 March 1918, the Germans attempted a breakout through the Michael Offensive, which was part of the much larger German spring offensive; the AIF suffered 15,000 casualties due to this effort. During this operation, Australian troops conducted a series of local defences and offensives to hold and retake Villers–Brettoneux over the period 4 to 25 April 1918. After the cessation of offensives by the German Army, the Australian Corps began participating in "Peaceful penetration" operations, which were localised raids designed to harass and gain small tracts of territory; these proved so effective that several major operational objectives were captured. On 4 July 1918, the Battle of Hamel saw the first successful use of tanks alongside Australians, with the battleplan of John Monash completed three minutes over the planned 90 minute operation. Following this success, the Battle of Amiens was launched on 8 August 1918, in conjunction with the Canadian Corps and the British III Corps, and concluded on 12 August 1918; General Erich Ludendorff described it as "the black day of the German Army".