Complex sentence: On December 30,1905, a bomb at his front gate assassinated Idaho's ex-Governor, Frank Steunenberg, who had gained the enmity of the union when he sent troops in to enforce martial law during the 1899 violence.
Split into simpler sentences: On December 30,1905, a bomb at his front gate assassinated Idaho's ex-Governor, Frank Steunenberg. Steunenberg had gained the enmity of the union when he sent troops in to enforce martial law during the 1899 violence.