Complex sentence: During the last period of the war, in 1644 Ferdinand III gave all rulers of German states the right to conduct their own foreign policy ("ius belli ac pacis")--the emperor hoped to gain more allies in the negotiations with France and Sweden.
Split into simpler sentences: During the last period of the war, in 1644 Ferdinand III gave to all rulers of German states the right to conduct their own foreign policy ("ius belli ac pacis"). This way the emperor was trying to gain more allies in the negotiations with France and Sweden.