In 1842 a series of attacks by bushrangers on homesteads in the Plenty River area north of Melbourne led to the first calls for a volunteer force.

It was suggested that the force be called the 'Port Phillip Volunteers'. Twelve military districts were envisaged, each to be commanded by a former army captain. The volunteers would dress in a green uniform and be heavily armed with a rifle, two pistols and a sword.

However, it was illegal to raise an armed force anywhere in the British Empire, except with the express approval of the Crown, and a special parliamentary act was required. Twelve years later, in 1854, Governor Sir Charles Hotham approved an Act to establish a Volunteer Corps not exceeding 2000 men, with officers appointed by the Governor. The force was independent from the regular British units, which maintained a presence until 1870.

The first unit formed was the Melbourne Volunteer Rifle Regiment, followed shortly afterwards by the Richmond Rifles, the Emerald Hill Rifles, the East Collingwood Rifles and the Fitzroy Rifles. Cavalry, Artillery, Engineer, Torpedo and Signal units quickly followed, named after the localities in which they were raised. All units were voluntary, with service part-time and unpaid. By 1860, the Act had been amended to allow a Volunteer force of 10,000.

The volunteer forces were disbanded in 1884, replaced by a 'Militia' organisation. The Militia were paid, and enrolled for a fixed term. Mounted Rifles and Victorian Rangers - The Victorian Mounted Rifles - were established a year later, and a Permanent Artillery Corps (or the Victorian Artillery) was formed in 1870.

References:
Marmion, B. (2003). 'The Victoria Volunteer Force on the central Victorian Goldfields, 1858-1883', MA Thesis, Latrobe University Bendigo.
Miller, T.(1957). 'The History of the Defence Forces of the Port Phillip District, 1836-1900', unpublished MA dissertation, School of History, University of Melbourne.
National Archives of Australia website: http://www.naa.gov.au/about-us/publications/fact-sheets/fs134.aspx

More Information