German foreign minister at the time of the Treaty of Versailles, and one of the architects of German-Soviet understanding in the 1920s.

As German minister in Copenhagen (1912–18), Brockdorff-Rantzau supported the Danish policy of neutrality during World War I and was able to maintain German-Danish trade. At the Conference of Paris in 1919 he argued in vain for better conditions of peace for Germany. Unable to dissuade his government from ratifying the Treaty of Versailles, he resigned his post as foreign minister in June 1919. In 1922 he became ambassador to the Soviet Union, where he and Soviet statesman Georgy V. Chicherin (Chicherin, Georgy Vasilyevich) worked to consolidate the German-Soviet rapprochement inaugurated by the Treaty of Rapallo. The German-Soviet Treaty of Berlin (April 1926) counterbalanced the Locarno Pact of 1925, which had seemed to link Germany too closely with the Western powers.