The cities of Cracow, Posen, and Lublin, especially susceptible on account of their German population, were thoroughly infected before 1522.

Next, the contagion attacked the country districts and towns of Prussia, which had been pretty thoroughly converted prior to its secularization.
The first political effect of the Reformation was to {141} stimulate the unrest of the lower classes.

Riots and rebellions, analogous to those of the Peasants' War in Germany, followed hard upon the preaching of the "gospel." Sigismund could restore order here and there, as he did at Danzig in 1526 by a military occupation, by fining the town and beheading her six leading innovators, but he could not suppress the growing movement.

For after the accession of the lower classes came that of the nobles and gentry who bore the real sovereignty in the state.

Seeing in the Reformation a weapon for humiliating and plundering the church, as well as a key to a higher spiritual life, from one motive or the other, they flocked to its standard, and, under leadership of their greatest reformer, John Laski, organized a powerful church.
The reign of Sigismund II [Sidenote: Sigismund II, 1548-1572] saw the social upheaval by which the nobility finally placed the power firmly in their own hands, and also the height of the Reformation.