Complex sentence: Despite being late comers to the organised resistance FTP became the first resistance group in France to deliberately kill a German and the PCF's electoral success after the Second World War was, to a large extent, due to its prestige as a centre of resistance.
Split into simpler sentences: Despite being late comers to the organised resistance FTP became the first resistance group in France to deliberately kill a German. The PCF's electoral success after the Second World War was, to a large extent, due to its prestige as a centre of resistance.