Paradoxically, to a certain extent, the biggest success story in a peace / disarmament process in history comes from the break-up of the Soviet Union.
Never in history an Army of HUNDREDS of thousands of effective soldiers retreated peacefully and voluntarily without being defeated. In just a handful of months almost half a million of Red Army soldiers left eastern european countries and former USSR republics.
It goes much to the credit of the heavily criticized political leadership of the time (Gorbachev before and Yeltsin afterwards) the fact of having avoided a bloodshed in Yugoslavian style.
Political leadership is key, this is the only answer, imho.