The same year, her father presented Ostfriesland with a trading treaty and a marriage alliance. Ostfriesland was chosen because it was strategically placed toward Denmark, and because the Calvinistic Emden was a rival to Lubeck and a treaty could break the domination of the Hanseatic league in Sweden.[2] In 1557, the trading treaty was completed, and in 1558, Edzard visited Sweden to meet Catherine and her sister Cecilia and chose one of them to complete the marriage treaty.