The
German-Soviet Frontier Treaty was a second supplementary protocol, of the 1939
Hitler-Stalin Pact (known as the
German-Soviet Treaty of Nonaggression, or by its original name of the
German–Soviet Treaty of Friendship, Cooperation and Demarcation). It was a secret clause as amended on September 28, 1939 by
Nazi Germany and the
Soviet Union after their
joint invasion and occupation of sovereign Poland. It was signed by
Joachim von Ribbentrop and
Vyacheslav Molotov, the
foreign ministers of Germany and the Soviet Union respectively, in the presence of Joseph Stalin. The treaty was a follow-up to the first secret protocol of the
Molotov–Ribbentrop Pact signed on August 23, 1939 between the two countries prior to their invasion of Poland and the start of
World War II in
Europe. Only a small portion of the protocol which superseded the first treaty was publicly announced while the spheres of influence of Nazi Germany and the Soviet Union remained classified. The third secret protocol of the Pact was signed on January 10, 1941 by Friedrich Werner von Schulenberg, and Molotov, whereas Germany renounced its claims to portions of Lithuania, only a few months before their anti-Soviet
Operation Barbarossa.