Never get into a religious spat in Prague next to an upper story window. On July 30, 1419 a Hussite mob tossed the town council out of the window of the town hall where many were lynched. The First Defenestration of Prague set off the Hussite Wars. It took 20 bloody years for the radical Hussites to be defeated but the Hussites were not completely eliminated. Needless to say Bohemia turned out to be very receptive to the doctrines of the Protestant reformation.
The decades after the reformation were periods of conflict between the largely protestant Bohemian nobility and their new (and very Catholic) Hapsburg monarchs. Complicating matters was the right granted to princes of the Empire by the Peace of Augsburg to impose their faith on their subjects. Yet the disagreements did not lead to war as the Hapsburg Emperors of the late 16th century chose to give their Bohemian subjects religious freedom. However matters came to a head in the last years of childless the Emperor Matthias. His heir was his cousin Ferdinand of Styria who advocated the Catholic counter-reformation and was not disposed towards religious freedom for his Bohemian subjects. Yet the Bohemian diet elected Ferdinand as King in 1617 (the extinction of the native royal houses of Bohemia, Poland and Hungary in the 14th and 15th centuries had made those monarchies elective).
The initial disagreement of the Bohemian Estates with Ferdinand was whether the religious freedom granted them allowed them to build Protestant churches on crown land. Ferdinand disagreed and had Emperor Matthias stop the construction and churches and declared the assemblies dissolved.
On May 23, 1618 four Catholic Regents appointed by Ferdinand in Bohemia met with representatives of the dissolved estates in Prague castle. The protestant lords wished to discover whether the regents were responsible for King Matthias’s order to cease construction of Protestant churches. Two of the regents thinking they would only be imprisoned admitted their responsibility. They were wrong.
To make an example of those who would interfere with their religion the two regents and their hapless secretary were tossed out of the third floor window (70 meters high) what was supposed to be to their death.
Catholics would claim that the three were saved by angels who helped them float down. Protestants would claim that they survived because they landed in a pile of manure. They may have been saved by their coats and the uneven castle walls slowing their fall.
This event made war unavoidable. When Matthias died in 1619 the estates deposed Ferdinand and elected Frederick V Elector Palatine and son in law of King James of England as King. Ferdinand would not take this lying down and his military response and overreaction to his victory would set off the Thirty Years War.