Unable to afford an army commission, he studied medicine in Dublin from 1882 to 1887 under auspices of the Royal College of Surgeons in Ireland.

His fiancée, Harriett Eveline Waters of Kildare, arrived two years later, and they were married on the day she landed, 20 May 1890, in St Philip's Anglican Church, Sydney.

Meredith became a government medical officer and joined the Hunter River Light Horse.

On 28 August 1914, Meredith joined the Australian Imperial Force as commander of the 1st Light Horse Regiment as a lieutenant colonel.

The 1st Light Horse regiment arrived back in Alexandria on 27 December 1915 and on 14 January 1916 was ordered to join the Western Frontier Force, defending the Sudan against the Senussi.

Meredith commanded the 1st Light Horse Brigade at the Battle of Romani in early August 1916, when his men fought off a series of Turkish attacks.

He left Australia for Egypt again on 9 December 1916, sailing from Melbourne and arriving back at Suez on 19 January 1917.

He boarded the transport on 12 November 1917 and arrived back in Australia on 20 December 1917, where his appointment to the AIF was terminated on 3 January 1918.

2 years later, he married 20-year-old Alice Christina Mowbray Windeyer on 19 October 1921, at St John's Anglican Church, Raymond Terrace.