Spanning from 1618 to 1648, the Thirty Years’ War remains one of the longest conflicts in human history. Fought across continental Europe, it resulted in over 8 million casualties, a figure which includes civilians who perished of starvation from resulting famines. Initially begun as a religious war between Catholics and Protestants, its ultimate purpose was to establish dominion across Europe.

Many scholars regard the war as an extension or byproduct of the Protestant Reformation, which began in the 1500s and sought to legitimize Protestant faiths, Calvinism and Lutheranism. In 1555 the Peace of Augsburg allowed nations to choose whether to adopt Protestantism or Catholicism. In response, Emperor Ferdinand II assumed the position of the head of state of the Holy Roman Empire in 1619 and sought to force all citizens to convert to Catholicism. This move was especially unpopular in the Bohemian states, Czechoslovakia and Austria. In 1618, the Bohemian states flung one of Ferdinand’s representatives out of a castle window. The Bohemian states quickly called for a revolt against Ferdinand, looking to Germany as an ally, while Ferdinand sought allegiance with Spain, a Catholic nation. Ultimately, France, Sweden, and Denmark would also become involved.

The war was a complicated one, with a separate series of battles fought between nationalized armies as well as private ones.