Complex sentence: On the evening of 15 January 1919 Rosa Luxemburg and Karl Liebknecht were discovered in a Berlin-Wilmersdorf apartment, arrested and handed over to the largest Freikorps, the heavily armed Garde-Kavallerie-Schützen-Division.
Split into simpler sentences: On the evening of 15 January 1919, Rosa Luxemburg and Karl Liebknecht were discovered in an apartment of the Wilmersdorf district of Berlin. They were immediately arrested and handed over to the largest Freikorps, the heavily armed Garde-Kavallerie-Schützen-Division.