Complex sentence: The picketing of the fuel depot--out of which tens of thousands of tons of coke were being distributed nationwide--became a pivotal, and symbolic, event during the strike and forcing its closure secured victory for the National Union of Mineworkers (NUM).
Split into simpler sentences: The picketing of the fuel depot--out of which tens of thousands of tons of coke were being distributed nationwide--became a pivotal, and symbolic, event during the strike. Forcing its closure secured victory for the National Union of Mineworkers (NUM).