After a 44-day bloody civil war in 1948, the rebel fighters of Costa Rica banned the country from having a standing army. Other than conquered nations under the dominion of another, is there any self-ruling nation that has ever fully disbanded its armed forces?
There is a current List of Countries with no Armed Forces on Wikipedia.
Before the 20th century, most armies were private or answerable to only individuals, not the state. You assume men fight for "countries", but even today many armies fight for a leader, not a country. To enumerate some of the armies or non-armies of the past:
(1) The Constitution of the United States forbids maintenance of standing armies and until the time of the Civil War, the United States had no standing army.
(2) Many small principalities like Ragusa, San Marino, Andorra, etc. have or had little or no army. Lichtenstein has had no army at all since 1939.
(3) Until about the time of the English Civil War, England had no standing army. The king relied on the fealty of his subjects. He would have to raise an army if he wanted to start a war. Moreover, the army was considered the army of the king, not of England.
(4) In Europe the situation was the same. Different princes would raise armies at different times for different purposes, but if a state was at peace, then often there was no army. Once again, when armies were raised, they answered to the prince or king or to whoever paid them.
(5) In ancient Greece, none of the city states had armies. If a war occurred, an army would be formed and a strategos would be appointed to lead it. After the war was over, all the men would go home.
(6) Ancient Rome was the same way. Until the time of Marius, about 100 B.C., Rome had no permanent legions, and only formed them at such time as they were needed.
(7) A book written in England in 1727 listed the following as the nations without standing armies: "Poland, Biscay, Switzerland, the Grisons, Venice, Holland, Genoa, Geneva, Ragusa, Algiers, Tunis, Hamborough, Lubeck, all the free towns in Germany, and England and Scotland until the late reigns."