Frederick was, especially in his youth and unlike his father, belligerent and adversarial, aroused by honor and national pride, and so he began his reign auspiciously with a campaign under the aged Johan Rantzau, which reconquered Dithmarschen. However, after miscalculating the cost of the Northern Seven Years' War, he pursued a more prudent foreign policy. The remainder of Frederick II's reign was a period of tranquillity, in which king and nobles prospered, and were Frederick instead focused more on hunting and feasting with his councillors as well as architecture and science. The period saw a great number of architectural constructions, including the royal castles of Kronborg at Elsinore and Frederikborg Castle at Hillerød.