High Quality Content by WIKIPEDIA articles! The Anglo-Polish military alliance refers to agreements reached between the United Kingdom and the Polish Second Republic for mutual assistance in case of military invasion by "a European Power". According to the secret protocol added to the treaty the phrase "a European Power" used in the Agreement was to be understood as Germany. It was signed in London on August 25, 1939. It was registered in League of Nations Treaty Series on January 3, 1940.