Complex sentence: Denmark's history has particularly been influenced by its geographical location between the North and Baltic seas, a strategically and economically important placement between Sweden and Germany, at the center of mutual struggles for control of the Baltic Sea ("dominium maris baltici").
Split into simpler sentences: Denmark's history has particularly been influenced by its geographical location between the North and Baltic seas. This meant that it was between Sweden and Germany and thus at the center of the mutual struggle for control of the Baltic Sea ("dominium maris baltici").