Moreover, the excellence of their colleges in foreign lands induced many of the nobility to send their sons to be educated under them, and thus were prepared the seeds of the Counter-Reformation.
The death of Sigismund without an heir left Poland for a time masterless.

During the interregnum the Diet passed the Compact of Warsaw by which absolute religious liberty was granted to all sects--"Dissidentes de Religione"-- without exception.

[Sidenote: January 28, 1573] But, liberal though the law was, it was vitiated in practice by the right retained by every master of punishing his serfs for religious as well as for secular causes.

Thus it was that the lower classes were marched from Protestant pillar to Catholic post and back without again daring to rebel or to express any choice in the matter.
The election of Henry of Valois, [Sidenote: Henry, May 11, 1573] a younger son of Catharine de' Medici, was made conditional on the acceptance of a number of articles, including the maintenance of religious liberty.

The prince acceded, with some reservations, and was crowned on February 21, 1574.