Described by Charles Bean as "short and dapper in figure, a vigorous, brave, upright and understanding leader of fighting men", William Birdwood commanded the Australian Corps for much of the First World War. He was born on 13 September 1865 in India and was educated in England.

He attended the Royal Military College Sandhurst before being posted back to India where he served on the north-west frontier. During the Boer War Birdwood served on Lord Kitchener's staff. He was awarded the Distinguished Service Order in 1908 and in 1911 was promoted to major general. Birdwood's career was characterised by a series of successful postings and steady promotion. When the First World War began, Britain's Minister for War, Lord Kitchener, placed Birdwood in command of the Australian and New Zealand forces bound for Europe. Before they reached England, however, the ANZACs, as they would soon be known, were ordered to disembark for training in Egypt. Birdwood met them there in December 1914.

Four months later Birdwood's troops landed at Gallipoli. He impressed the men by regularly visiting the front lines and taking daily swims in the sea, heedless of the danger from Turkish shrapnel aimed at men seeking such refreshment. His bravery earned Birdwood the enduring respect of the AIF, and he was appointed its temporary administrative commander, as well as its operational commander, following the death of General William Bridges in May 1915. The appointment was made permanent in September 1916.

Having watched all attempts fail to make headway against the Turks on Gallipoli, Birdwood was nevertheless opposed to the evacuation when the question was raised. In this he was overruled and he oversaw the successful withdrawal in December 1915. In early 1916 the ANZAC Corps was split in two. Birdwood assumed command of I ANZAC Corps, accompanied it to France, and directed its operations throughout 1916 and 1917.

Birdwood made a point of appointing Australians to command and staff positions but took command of the Australian Corps when it was formed from the five AIF divisions in November 1917. He was succeeded by Lieutenant General John Monash in May 1918 and took command of the British 5th Army, but still retained command administrative command of the AIF with the support of almost all senior Australian officers. Despite his having commanded Australians through some of the Western Front's more disastrous actions, Bullecourt being one example, Birdwood continued to be held in high regard. His willingness to support those he commanded, to argue on their behalf and indeed to make it known that he had done so, earned Birdwood a respect from Australians that was given to few British senior commanders.

In 1920 Birdwood was made a general in the Australian Military Forces and five years later was made field marshal. He toured Australia and New Zealand in 1920 to wide public acclaim and was given command of the Indian Army in 1925. He retired from the military in 1930 and was thwarted in his desire to become Australia's Governor-General when the prime minister insisted on the office being held by an Australian. Birdwood died in England in 1951 and was buried with full military honours.