Alfred Winter ,'Group of military volunteers', c 1880 (W.L. Crowther Library, SLT)

Defence, in terms of resistance to invasion, was a life and death issue for Aboriginal Tasmanians in the first thirty years of the nineteenth century. The initial indications that resistance (or perceived resistance) to occupation would be met by military force occurred at Risdon and Port Dalrymple in 1804. Aboriginal guerrilla resistance gradually increased as the settled area expropriated their hunting grounds. During the 1820s a variety of military efforts were employed against them, culminating in the failed attempt of the Black Line to drive them into the Tasman Peninsula, soon followed by George Robinson's missions, which brought Aboriginal military defence of their land to an end. (See also Frontier Conflict.)

British settlements on the Derwent and Tamar Rivers were designed to beat the French to Van Diemen's Land and protect the sea route to New South Wales. However British infantry units in the colony were never used against external threats. Instead soldiers fought against Aborigines and bushrangers, especially between 1814 and 1825, and performed guard duty at penal settlements. At various times the defence force itself created social dissension, notably in 1845 when about fifty soldiers wrecked hotels and assaulted civilians in an hour's rampage through central Launceston.

The end of transportation and introduction of self-government coincided with British interest in reducing imperial garrisons, which meant colonies assuming greater responsibility for defence. Tasmanians showed little interest, and the first volunteer units, formed in 1859 in Hobart and 1860 in Launceston, received scant government encouragement. The withdrawal of British military forces in 1870 did nothing to encourage Tasmanian self-reliance. For the rest of the nineteenth century the only active responses to local defence were moulded by British imperial concerns. In particular, Russian scares in the late 1870s and mid-1880s prompted a modest revival of volunteer forces, whose vigour and commitment were largely responsible for the purchase of a torpedo boat (which arrived in Hobart in 1885, but was rarely operational, finally going to South Australia in 1905), for developing plans for mining the Derwent, and for completing artillery batteries in southern Tasmania in 1885 (Queen's, Alexandra and Kangaroo Bluff Batteries). Several Tasmanians enlisted in the New South Wales contingent which went to the Sudan in 1885, the first Australian unit to serve overseas in an imperial war.

However, it was the South African (Boer) War which really established the pattern of overseas military service as the essential element in defence throughout the Australian colonies. The frontline of Tasmanian defence since 1899 has always been on foreign battlefields. About 860 Tasmanians served in the South African war (1899–1902). From 1901 to 1914, Tasmanian defence continued in the hands of a small voluntary force. A cadet system developed, and universal military training for males between the ages of 12 and 26 was introduced in 1911, but citizen units formed the basis of Tasmania's military contribution during the First World War.

Although the war opened deep divisions in the community, there was almost universal agreement that Tasmanian interests were tied to the needs of the British Empire and that it was necessary for Tasmanians to fight overseas to help win the war. More than 13,000 Tasmanians embarked, as members of many different units, including about 80 nurses and over 100 members of the Air Flying Corps, and others in the Royal Australian Navy, but nearly 75 percent were members of the infantry units of the Australian Imperial Force (AIF), the 12th, 40th, 26th and 15th Battalions, and the main artillery unit, the 3rd Field Artillery Brigade. The cost was high. More than half of these Tasmanians were casualties, 2432 being killed, and many more wounded in body and spirit.

Between 1919 and the mid-1930s the issue of defence became increasingly unimportant, although the identities of Tasmania's main AIF battalions were retained in a citizen militia, based around the 12th Battalion (Launceston) and 40th Battalion (Hobart). Defence forces in Tasmania were undermanned and poorly resourced, as people reacted to the war years, and as compulsory military service was dismantled, and finally abolished in 1929.

During the Second World War, Tasmania's defence interests were again universally perceived as being served by contributing men and material to fight elsewhere. Tasmania itself, unlike other areas of Australia, was officially regarded as an 'isolated locality', not a likely target for attack or invasion, a view generally shared by the public. However, 5000 people joined the Civil Defence Legion by the end of 1940, and Japan's entry into the war in December 1941 sharpened fears of air raids and submarine attacks. About 31,000 Tasmanian men and women enlisted in military forces, more than two-thirds joining the army. The majority served outside Tasmania, either overseas or other parts of Australia, and 1066 were killed. A high proportion of the civilian population (in the workforce and as volunteers) was engaged in defence-related work, creating full employment as industry and agriculture were reorganised and expanded to meet war needs.

From 1945 to the mid-1970s the significance of defence ebbed and flowed in conjunction with developments in the Cold War and perceived communist threats. Citizen forces were revamped and reorganised in reaction to national military exigencies. National service for home defence was introduced during the Korean War, in which about 600 Tasmanians fought, and 22 men were killed. War in Vietnam resulted in Tasmania's largest military contribution since the Second World War, more than 1500 Tasmanians serving there between 1965 and 1974, 704 of them conscripted national servicemen. Seventeen Tasmanians were killed, and another two Tasmanians were killed in the earlier Malay–Borneo conflict. The introduction of conscription during the Vietnam War witnessed another reorganisation to accommodate an increase in numbers, and from 1972 the tradition of the 12th and 40th nomenclature was revived, at times in amalgamation, such as in 1987 when the 12th and 40th Independent Rifle Companies were amalgamated with other units to form the 12/40th Royal Tasmanian Regiment.

Since the Vietnam War ended, further reforms have created the Army Reserve and Ready Reserve in attempts to forge closer operational capacity with regular forces, and there have been expanded opportunities for women in all military services, but there has also been a steady attrition of the main functional elements of defence from Tasmania, such as training, to more specialised facilities in other states. In the early twenty-first century Tasmanians continued to serve overseas, in places such as Timor and Iraq, but the island's 'isolated locality' is as true as it has been for most of the time since the South African War. Skeleton military services are maintained, particularly concerned with recruitment, and are based mainly in Australia's oldest military establishment, Anglesea Barracks in Hobart.

Peter Henning