Complex sentence: It was built by Siemens predecessor Siemens-Schuckert near the town of Bobrek, Poland, it held approximately 250-300 prisoners who were used as slave labor to produce electrical parts for aircraft and U-boats.
Split into simpler sentences: It was built by Siemens predecessor Siemens-Schuckert near the town of Bobrek, Poland. IT held approximately 250-300 prisoners who were used as slave labor to produce electrical parts for aircraft and U-boats.