Complex sentence: Armed conflict in the eastern Slavonia, culminating in the Battle of Vukovar and subsequent massacre, also included heavy fighting and successful defence of Osijek and Vinkovci until the front line stabilized as a ceasefire was agreed on 2 January 1992, coming into force the next day.
Split into simpler sentences: Armed conflict in the eastern Slavonia, culminating in the Battle of Vukovar and a subsequent massacre, also included heavy fighting and the successful defence of Osijek and Vinkovci. The front line stabilized and a ceasefire was agreed to on 2 January 1992, coming into force the next day.