This is from an excellent paper by Andrej Kokkonen and Anders Sundell in CPS:
Leadership succession is a perennial source of instability in autocratic regimes. Despite this, it has remained a curiously understudied phenomenon in political science. In this article, we compile a novel and comprehensive dataset on civil war in Europe and combine it with data on the fate of monarchs in 28 states over 800 years to investigate how autocratic succession affected the risk of civil war.
Exploiting the natural deaths of monarchs to identify exogenous variation in successions, we find that successions substantially increased the risk of civil war. The risk of succession wars could, however, be mitigated by hereditary succession arrangements (i.e., primogeniture— the principle of letting the oldest son inherit the throne). When hereditary monarchies replaced elective monarchies in Europe, succession wars declined drastically. Our results point to the importance of the succession, and the institutions governing it, for political stability in autocratic regimes.
There are important lessons here, too, for young democracies. The paper is a reminder that the responsible thing to do while promoting electoral competition in young democracies is to also invest in the institutional mechanisms that facilitate the peaceful conduct of elections and that enforce the outcome of elections.