The Treaty of Neuilly, strictly the Treaty of Neuilly-sur-Seine, was signed with Bulgaria after World War One had ended. The treaty was signed on November 27th 1919.As Bulgaria had been one of the allies of Germany during World War One, the victorious nations were in no mood to be either sympathetic or charitable to Bulgaria.As with the other settlements after the war, land was taken from Bulgaria and reparations were required.hen World War Two broke out, Bulgaria sided with Nazi Germany and reclaimed all the land taken from her by the Treaty of Neuilly. By the time World War Two ended, Bulgaria’s effective independence was also ended.