The son of John Donaldson and Elizabeth, nee Lever, Alexander Donaldson was born on 6 September, 1873, at Diamond Creek Victoria. He had one sibling, his sister Annetta, b. 1971. By 1917, when he enlisted, he was a factory manager, married to Gertrude, and living at 112 Grey Street, East Melbourne. They appear to have had no children. Alexander Donaldson enlisted on 8 October, 1917, and was sent to Broadmeadows for training to Broadmeadows, where he was placed in the 1st Depot Battalion, Sports Unit. After initia training, he was placed in the 14 Reinforcements of the 29th Battalion and embarked for England on HMAT Ulysses A38 on 22 December, 1917.

Alexander Donaldson disembarked at Southampton on 15 February, 1918, just as the German Army was beginning their Spring Offensive, and marched into Codford to be taken on strength with the 15th Training Battalion. On 29 April, the reinforcements left from Folkestone for Havre and then to the AIB Depot. On 6 June, 1918, Alexander Donaldson was finally taken on strength with the 29th Battalion. The 29th Battalion was part of the 5th Division and was fighting against the German Spring Offensive, the last great push for Germany, using the soldiers released form the Eastern Front following the Russian Revolution to reinforce the Western Front Battalions. It was a calaculated gamble, taken before United States troops could reinforce the Allied Forces. The Spring Offensive moutned three major attacks, first at Arras in the Somme region in March, then at Lys in Flanders in April-May and finally at the Marne mid-June. Following this came the Allied push to the Hindenburg Line, the last major action of the war. On 17 October, 1918, Alexander Donaldson became ill and was sent to hospital. Following this, he was transferred across to the 32nd Battalion, which was resting and retraining away from the main action when peace came on 11 November, 1918. On 17 March, 1919, he was sent home, suffering from rheumatism and discharged from further service on 3 May, 1919.

It is difficult to track him after this. In 1936, he was livng at 15 Gage Street Holmesdale, Magill, South Australia, when he wrote to the military authorities, but his name is too common to track him through the Electoral Rolls. He died at Bright, Victoria, in 1958, aged 85.