Complex sentence: On 17 July 1941 the German occupational authority, the Reichskommissariat Ostland, was created, and soon afterwards, on 20 July, the Minsk Ghetto was established.
Split into simpler sentences: On 17 July 1941 the German occupational authority, the Reichskommissariat Ostland, was created. On the 20th, the Minsk Ghetto was established.