Frederick was committed to becoming the mightiest king in the North, and for several years he fought exhausting wars against his archrival Erik XIV of Sweden, after which the battles changed character. It's was now a competition to see who could trace their family history the furthest, and who could construct the most formidable castles. In the 1570s he constructed Kronborg, a large Renaissance castle that became widely recognized abroad, and its dance hall was the largest in Northern Europe at the time. He enjoyed entertaining guests and throwing elaborate festivities, which were well-known throughout Europe. During the same period, the Danish fleet was developed into one of Europe's largest and most modern. As part of his efforts to strengthen the kingdom, he provided much support for science and culture.