In 1969 his party formed a new coalition with the Social Democrats. He became Foreign Minister and Vice Chancellor. With Willy Brandt his foreign policy meant the Federal Republic of Germany promised not to try and get back the parts of Germany given to Poland and the USSR. The treaty with Poland actually defined the western border of Poland, not the border between Poland and Germany. It is the same thing, but meant Poland could sign a treaty with West Germany that described the border of East Germany.