Andrew McNiven enlisted on 29 September, 1916. He was the son of David McNiven, Cheltenham House, Cheltenham, Victoria, and gave as his address 226 Clarendon St., East Melbourne. By trade, he was a draper, an occupation he maintained post-war. He was a single man, aged 31 and 11 months, 5' 4" tall, with grey eyes and brown hair. By religion, he belonged to the Church of England. 

At the time he joined the A.I.F., the war was on the Western Front, engaged in the Battle of the Somme and specifically, the Battle of Verdun (21 February - 18 December 1916), with massive slaughter on both sides.The battle was the longest of the First World War. In 2000, Hannes Heer and Klaus Naumann calculated the French losses at 377,231 casualties and the Germans 337,00, a total of 714,231 and an average of 70,000 a month.`

Andrew McNiven was initially placed with the Depot Reserves in the Domain, Melbourne, then embarked from Melbourne on 16 December, 1916, on H.T. Medic, disembarking at Plymouth on 18 February, 1917. From here, he was sent to Hurdcott Military Camp and placed with the 8th Training Battalion. On 23 June, he left England from Southampton to join the army in France,landing at Le Havre, and was taken on strength with the 29th Battalion. From the 29th Battalion, he was shifted to the 39th Battalion on 14 July, joining his new battalion on 18 July

There is nothing in his record to tell where he was from July 1917 to 2 February, 1918, when he was given leave in England, rejoining the 39th Battalion on 23 February. The history of the 39th Battalion, however, says they fought their first battle at Messines in Belgium on 7-9 June, 1917. They suffered heavily from gas attacks from the German troops, so that less than a third of the troops was able to attack, but these brave men captured their objective in spite of the level of casualties. This may explain why Andrew McNiven was shifted to the 39th only 4 days after being assigned to the 29th Battalion. He would have been there for the battle of Broodseinde on 4 October and the disastrous Battle of Passchendaele on 12 October. 

For the next five months, the 39th Battalion rotated between service in the rear areas and the front line. Andew McNiven would have been back from leave when Germany launched its Spring Offensive on 1918, and the 39th Battalion was rushed south from Belgium to France and played a role in turning the German  troops away from their goal to capture the vital railway junction at Amiens.

He must have done well in these battles, because on 29 June, 1918, he was detached for duty back in England, and took a Senior Officers Course, disembarking at Folkestone to report to Farnsborough. Here he was attached to the Senior Officers Course at Aldershot, then serving there as a Batman. On 8 August, he had another two weeks of leave, 10-23rd August.

His time at the front was not finished yet; on 29 September, he was sent from Folkestone back to France on completion of his duty in England, rejoining his battalion in the field on 5 October, 1918, only five weeks from the end of the war on 11 November, 1918. He was not released from service when that day came, but stayed on in France for another six months. On 8 May, he finally sailed back to England from Le Havre, marching into camp at Codford. On 9 May, he boarded a ship for home, disembarking in Melbourne on 11 October, 1919.

Andrerw McNiven resumed his trade as a draper, living for many years at 26 High St., Prahran. In 1942, he married Florence Mary Critten. He died in 1954, aged 74, and was interred privately at Cheltenham Cemetery.