premise: After rival Fujiwara factions had been struggling for years to gain control of the imperial throne, they turned to the Taira and Minamoto armies in 1156 to wage the four-year war that heralded the end of the golden age of the Heian court.
hypothesis: After rival Fujiwara faction had struggled for years to gain power, they waged a four year war that ended the golden age of the Heian court.