Tyrannies, compared to democracies, are more likely to cause wars. Tyrannies violate human rights and these violations make it very difficult to maintain the rule of law (different human rights institute the rule of law, and the indivisibility of human rights means that the whole body of human rights is in danger when some human rights suffer). Without the rule of law, it is very hard to maintain a justice system which that can channel conflicts away from violence. As a consequence, these conflicts can escalate and can become violent. People start to take the law in their own hands. They start to steal, to compensate for goods stolen, and to murder, to compensate for murder. Revenge is seen as the only alternative for justice, and revenge tends to escalate. Large-scale conflict and civil war become a very real threat. And civil wars have a tendency to become international wars.
Moreover, violations of human rights create anger, frustration and revolt (this is true for all types of rights, economic rights included), and can therefore be a direct cause of civil war. And civil war can lead to international war.
However, there is an even more direct link between rights violations and international conflict. Rights violations can create tensions with neighboring countries because of refugee flows, which result from rights violations or civil war. Neighboring countries can decide to intervene in these rights violations or in a civil war, to protect their own safety and prosperity. This intervention can, of course, lead to an international conflict. It is, however, the internal situation in a country and not the intervention from the outside, which causes the conflict. It is the country in which human rights are violated, which creates international instability.