His two former Protestant allies, Maurice and John von Kuestrin, made an alliance with France and with other North German princes and forced the emperor to conclude the Convention of Passau.

[Sidenote: 1552] This guaranteed afresh the religious freedom of the Lutherans until the next Diet and forced the liberation of John Frederic and Philip of Hesse.

Charles did not loyally accept the conditions of this agreement, but induced Albert, Margrave of Brandenburg-Culmbach, to attack the confederate princes in the rear.

After Albert had laid waste a portion of North Germany he was defeated by Maurice at the battle of Sievershausen.

[Sidenote: July 9, 1553] Mortally wounded, the brilliant but utterly unscrupulous victor died, at the age of thirty-two, soon after the battle.