Tyrants need a war. Looking back over the past hundred years one finds that tyrants come to power in conflict and remains in power largely due to conflict. It centers the populace, distracting them from other societal challenges to include their civil liberties.
Politically weak or insecure leaders also need a distraction. I call those distractions boogeymen--nations, a peoples, or culture that the leader perceives to be a threat to the national security. This boogeyman also distracts from the political challenges both real and imagined that leader faces. Hitler had the Jews; Stalin capitalism; the Ayatollah the "Great Satin," and Assad "terrorists" by way of a few examples.
Dictators and other leaders need a populace that is afraid. Fear is a powerful psychological tool to govern with and leaders use it for various reasons. A populace that is afraid of "something" looks to its leader for security and a solution. This is where the shadow of a boogeyman is useful. Fear can bring a society together in common cause.
Historically these conflicts created by a tyrant, dictator or insecure leader rarely succeed. The immediate result may be a distraction, but in the long term that nation, and its leader, end up weakened and in some cases worse off than they were before the conflict. Various circumstances intervene that were unintended consequences. History shows that these unintended consequences rarely benefit a leader.