Bo Prefecture
However, prior to the princes' working out a coordinated plan, on September 16, 688, Li Chong launched a rebellion himself at Bo Prefecture (博州, roughly modern Liaocheng, Shandong), where he was serving as prefect. He notified Li Yuanjia, Li Yuangui, Li Lingkui, Li Zhen, and Li Shen (李慎) the Prince of Ji (Li Zhen's brother) and asked them to rise as well, but only Li Zhen did, as the other princes, not fully prepared, were hesitant to do so.
Read more about this topic: Li Chong (Tang Dynasty)