The story
Reformation in the Czech lands started already in the 15th century, one century before Luther's Reformation. At that time, most Czechs (~85%) were Protestant; there were two Protestant churches: the Utraquist Hussite Church (1431–1620) and the Unity of the Brethren (1457–1620). (The latter was in the 1720s partially renewed outside of Czech territory as the Moravian Church.) However, non-Catholic churches were forbidden in 1620 when the Bohemian Revolt was decisively defeated and victorious Habsburg rulers imposed harsh Counter-Reformation measures on the Bohemian Crown. This ban was mitigated in 1781 by issuing the Patent of Toleration that permitted Lutheran and Calvinist churches in the Habsburg monarchy but Protestants obtained full equality with the Catholic church legally only as late as in 1867, when Austria-Hungary was created. Nevertheless, other minor churches were still forbidden until the founding of Czechoslovakia in 1918.
The ECCB was established in 1918 by the unification of most Lutheran and Calvinist churches in Bohemia, Moravia, and Silesia. It was intended to be a successor of the Unity of the Brethren (and the Bohemian Reformation in general). Some Lutheran churches in Silesia chose not to join, forming instead the Silesian Evangelical Church of the Augsburg Confession. There were also initial talks of a merger with the Evangelical Church of the Augsburg Confession in Slovakia, but the merger was ultimately rejected since Slovak Lutherans felt the ECCB had a Czech nationalistic character, and the ECCB made no further attempts to establish itself in Slovak lands. The two churches still maintained close ecumenical relations.
From Wikipedia’s article on Evangelical Church of Czech Brethren, shared under CC BY-SA 4.0.4