Gorbachev resigned as president of the Soviet Union on December 25 1991, days after the leaders of Belarus, Russia and Ukraine said the USSR no longer existed. A former KGB agent and loyal servant of the Soviet Union, Putin was dismayed when it fell apart, once calling the collapse "the greatest geopolitical disaster of the 20th century". IMAGES of Moscow city center, Red square and Kremlin. SOUNDBITES of Moscow citizens.