During this era, the political centralization of the earlier Tibetan Empire collapsed.[22] The period was dominated by rebellions against the remnants of imperial Tibet and the rise of regional warlords.[23] Upon the death of Langdarma, the last emperor of a unified Tibetan empire, there was a controversy over whether he would be succeeded by his alleged heir Yumtän (Yum brtan), or by another son (or nephew) Ösung (’Od-srung) (either 843–905 or 847–885). A civil war ensued, which effectively ended centralized Tibetan administration until the Sa-skya period.