Complex sentence: From 2009 until October 2011, Lieutenant General Nikos Papagiannopoulos was Chief of Staff at the Headquarters, and in this capacity he oversaw staff planning and the central police services based in Athens.
Split into simpler sentences: From 2009 until October 2011, Lieutenant General Nikos Papagiannopoulos was the Chief of Staff at the Headquarters. In this capacity he oversaw staff planning and the central police services based in Athens.