Complex sentence: When the FI was reorganised after 1945 and again based in France the IS again became its leading committee and was dominated by the figures of Ernest Mandel (Germain) and Michel Raptis (Pablo).
Split into simpler sentences: When the FI was reorganised after 1945, again based in France, the IS again became its leading committee. It was dominated by the figures of Ernest Mandel (Germain) and Michel Raptis (Pablo).