Answer:
The Thirty Years' War, which lasted from 1618 to 1648, was a large-scale conflict that involved most European powers. The main causes were the tensions between Catholic and Reformed states, but geo-strategic motives also played an important role.
The war raged mainly in the Holy Roman Empire, the Spanish Netherlands, northern Spain and northern Italy with battles also in Africa and the American continent. There were also sea battles on the Mediterranean Sea and in the Bay of Biscay. Due to the strong geographical spread of the large-scale hostilities, it can be said that this war was the first global conflict or world war.
The conflict began when the Catholic states of Spain and Austria conquered the reformed states in the north of the Holy Roman Empire (Bohemia, the Palatinate, northern Germany and Denmark). Sweden and France actively intervened in to weaken Spain and Austria. The Peace of Westphalia ended the war.
As a direct result of the peace in Westphalia, Germany was divided into dispersed duchies, which, however, nominally belonged to the empire until its dissolution in 1806.
