The peace concluded by Gustavus with Russia in 1617 was accompanied by a fresh outbreak of the war with Poland; and this renewal of the contest with the old rival of his house naturally drew the king's attention to affairs in Germany; for Ferdinand, now rising into power, was the brother-in-law of Sigismund, and likely to give him what aid he could in his Swedish enterprise. And Gustavus, too, was not quite a foreigner in Germany. Through his mother German blood ran in his veins, and when, in the summer of 1618, he visited Berlin in secret, he was won by the lovely face of the daughter of that energetic Elector of Brandenburg who after boxing the ears of the rival candidate for the dukedom of Cleves had adopted the Calvinist creed and had entered the Union. The death of the Elector delayed the marriage, and it was not till 1620 that, on a second visit, Gustavus wrung a consent from the new Elector, George William, whose weakness and vacillation were to be a sore trial to the Swedish king in after years. In strict incognito, Gustavus travelled as far as Heidelberg, at a time when the Elector was far away, in the midst of his short-lived splendour at Prague. Gustavus learned something from that visit which he never forgot. He saw the rich luxuriance of that fair Rhine valley, stretching away till the western hills are but dimly visible in the blue distance, and which, compared by Venetian travellers to the green Lombard plain, must have caused strange sensations of wonder in the wanderer from the cold and barren north. And he saw another sight, too, which he never forgot--the wealth and magnificence of the Rhenish prelates. 'If these priests were subjects to the king my master' (he spoke in the assumed character of a Swedish nobleman) 'he would long ago have taught them that modesty, humility, and obedience are the true characteristics of their profession.' [Sidenote: § 7. His daring and prudence.] Plainly in this man there was something of Christian of Anhalt, something of the desire to overthrow existing institutions. But there was that in him which Christian of Anhalt was ignorant of--the long and calm preparation for the crisis, and the power of establishing a new order, if his life should be prolonged, to take the place of the old which was falling away. [Sidenote: § 8. Renewed war with Poland.] Gustavus returned to carry on the war with Poland with renewed vigour. In 1621 Riga surrendered to him. The next year he concluded a truce which gave him leisure to look about him. [Sidenote: § 9. His interest in the German war.]