 Complete the following phrase:  Over the centuries the ownership of the town changed frequently, as did the borders between different countries. After the foundation of the German Empire in 1871 the area became known as Dreikaisereck triangle of the three emperors, as it was situated at the point where the Austrian, German and Russian Empires adjoined. After World War I, in 1918, Poland regained independence, and in 1919, local Polish miners organized large protests in Mysłowice. On August 15, 1919, the German Grenzschutz opened fire on protesting Polish miners and their families. Seven miners, two women and a teenage boy were killed, and many people were wounded. The event, known as the Mysłowice massacre, sparked the 