"The Barbarian Invasions" ("Les invasions barbares"). With the brief exception of the Mongol invasions, major barbarian incursions ceased. Many came as refugees due to the Mongol invasions and conquests. These costly invasions and conquests and the introduction of paper currency caused inflation. Further damage occurred with the Barbarian invasions. This has traditionally been attributed to calamities such as plague, earthquakes and Slavic invasions. Warlords, revolutions, natural disasters, civil war and invasions contributed. These issues led to feuds, wars, trade competition and invasions. It was the beginning of many barbarian invasions. During the Migration Period and the Barbarian invasions, Zadar stagnated. The Pagan Kingdom fell due to the Mongol invasions and several warring states emerged. Significant urban settlements only developed following the period of Viking invasions. This provoked two Persian invasions of Greece. Georgia was further weakened by several disastrous invasions by Tamerlane. After the Japanese invasions, the Korean Peninsula was devastated.