Second generation Reformed churches

Reformed doctrine had already shown a greater capacity to mobilize popular support than Lutheran ideas when the two were in direct competition in the cities of south Germany. Now it also offered compelling reasons for those drawn to it to separate themselves from the church of Rome. It offered a model derived from the Bible of how to form independent churches in the absence of governmental support. It was firmly ensconced in a number of enclaves that were well situated to serve as bases for wider expansion and that appeared to contemporaries to be admirable models of reformed communities. Its theologians had given expression to its basic tenets in a number of monuments of compelling exegesis. With its diversity of ecclesiologies, it could justify magisterial control of a state church as well as the formation of independent churches under the cross, making it appealing to rulers who had already assumed the supreme headship within their territories.  All of these considerations help to explain why the Reformed churches were poised for a dramatic period of expansion in 1555.

Philip Benedict, Christ's Churches Purely Reformed:  A Social History of Calvinism, 120, summarizing the second generation of the Reformed tradition.  "Churches under the cross" refers to illegal churches meeting in secret in northern Italy.