Complex sentence: After the fall of Srebrenica in July 1995, Madeleine Albright, the U.S. Ambassador to the United Nations, told the UN Security Council that (the) whereabouts of some 6,000 Bosniak men and boys from Srebrenica was unknown.
Split into simpler sentences: After the fall of Srebrenica in July 1995, Madeleine Albright, the U.S. Ambassador to the United Nations, spoke before the UN Security Council. She said: (the) whereabouts of some 6,000 Bosniak men and boys from Srebrenica was unknown.