John (Jack) Simpson Kirkpatrick was born in 1892 at South Shields, North East England. On joining the army he dropped his last name and became simply "John Simpson", the name by which he is now generally  known. 

Simpson is one of the best-known soldiers of the First Australian Imperial Force. However, like many members of the AIF, he had actually been born in the UK at South Shields, County Durham, to Scottish parents.

In 1909 Simpson's father died and he joined the Merchant Navy at the age of 17, working as a stoker and steward. On 13 May 1910 he "jumped ship" at Newcastle, New South Wales. During 1911 Simpson was in Western Australia for a while and worked there on the Yilgarn Goldfield. He always sent money to his mother and sister in South Shields.

On 25 August 1914 in Perth, Western Australia, he joined the AIF and the Australian Army Medical Corps under the name "John Simpson", as a stretcher bearer. He was given the service number of 202 and underwent basic training at Blackboy Hill Camp. He was assigned to C Squadron, 3rd Field Ambulance. In the Army, his Geordie accent was mistaken for an Irish accent and he was nicknamed "Murphy".

Simpson and his mates were sent to Europe on board the SS Medic as part of a convoy. During the trip, the SS Sydney, one of the other convoy ships, sank the German raider, the "Emden".

The convoy stopped in Egypt instead of continuing to Europe because Turkey had joined the war and taken sides with Germany. The Suez Canal had to be protected. This was a great disappointment to Simpson who had been looking forward to spending Christmas Day in South Shields. On April 15th 1915, the Third Field Ambulance stretcher bearers were transferred to the troopship Devanha in preparation for landings on the Gallipoli Peninsula on 25th April 1915. On the afternoon of the 24th April, the invasion fleet steamed out of Mudros Harbour towards the Gallipoli coastline. The Third Field Ambulance were transferred to the destroyer Ribble.

Due to a navigational error, the ANZACs (Australian and New Zealand Army Corps) were put ashore approximately two kilometers north of their planned landing. As a result the soldiers faced a hostile terrain, dense undergrowth, steep cliffs, a 100-meter high rugged hill and Turks on the plateau above firing down on them.

Simpson's boat grounded almost opposite a rocky outcrop known as the Sphinx. Simpson found a donkey, which he named variously "Duffy", "Murphy" and "Abdul", that had been landed by a field artillery unit, and began operating independently. Simpson took off his Red Cross armband and tied it around the donkey's head. He told the men that as the donkey was now a member of the unit he would make it official. Simpson used the donkey to carry the wounded, using bandages to make a head stall and a lead rope. With his donkey and working all day and into the night, Simpson was making between twelve and fifteen trips a day between the front line and the shore.

Simpson refused to go back to his own unit at the end of each day's work, despite being ordered to return by his section sergeant. Simpson fed his donkeys by tying them up next to the mules of an Indian artillery unit. He camped and ate with the Indians of the 21st Kohat Mountain Battery. The Sikh gunners called him "Bahadur", which means "Bravest of the Brave".

After just a few weeks at Gallipoli, Simpson was hit by machine gun fire. He was 22.

John Simpson Kirkpatrick rescued about three hundred wounded soldiers during his twenty-four days of donkey trips down Monash Valley. He was buried at Hell Spit. A clergyman officiated and the grave was marked with a simple wooden cross with only his name on. After the Armistice, Simpson was remembered with a headstone in Beach Cemetery close to ANZAC Cove.

The final death toll for the Gallipoli Campaign was:
Australians 7,300, British 25,000, French almost 10,000, Turks 87,000, New Zealanders 2,400.
A horrific total of almost 131,700 men were killed.

The statue of Simpson and donkey (1988) by Peter Collett stands outside the Australian War Memorial, Canberra. There is another sculpture of Simpson and his Donkey by Wallace Anderson (1935) at the Melbourne Shrine of Remembrance.