The military history of Finland can be divided into four distinct periods. The first period being 'Pre-Swedish Era', the Second 'The Swedish Empire Era', Third 'Grand Duchy of Finland/Russian Empire Era' and the fourth being the 'Independent Republic of Finland/Modern Era'.
The Pre-Swedish Era consists of poorly documented battles, most coming from Nordic Sagas, Germanic/Russian Chronicles and Swedish Legends. Archaeological evidence shows Bronze Age (1500-500BC) Finns specialising in weapons such as the battle axe and swords, there are also indications of hill forts. Viking attacks from Sweden and Norway have been found with runic inscriptions as well as unhistorical sources.
The Swedish Empire Era which began officially ran from 1352 till 1808 in which Finnish soldiers fought in at least 38 wars of note for Sweden. Whether they be during the power struggles of the Swedish Royals or in wars between Sweden and other nations.
During the period in which Finland was known as the Grand Duchy of Finland; we see Finland changing hands from Swedish to Russian rule as a result of the 1808-1809 Finnish War. Fighting on its on soil against the British and French during the Crimean conflict and on the Eastern Front during the First World War.
From when Finland declared its independence in 1917 to present day it has been involved in a civil war, which saw the country torn apart by two opposing factors, the Reds (Communists) and the Whites (Right wing groups, Liberals and centralists, all allied and against Communist beliefs). The Kinship Wars in which Finland helped other Baltic states, the most notable being the Estonian War of Independence. There was also the Soviet Invasion of 1939-'40 which is known as the Winter War, this was soon followed by the joint Finnish and Nazi Germany attack on Soviet Russia (The Continuation War). When the Finns signed a peace treaty in 1944 with the Soviet Union they fought against their former German Allies in the Lapland war. Since the foundation of the United Nations in 1945, Finnish Troops have served in various peacekeeping operations.