Complex sentence: The Republican Left represented the Colonial lobby of the Opportunistic Republicans, they advocating for the expansion of the French Colonial empire and for peace with the German Empire, this was in direct contrast to the policies of the Radical Republicans.
Split into simpler sentences: The Republican Left represented the Colonial lobby of the Opportunistic Republicans. They advocated for the expansion of the French Colonial empire and for peace with the German Empire, which was in direct contrast to the policies of the Radical Republicans.