There was a period of massive cooling around 535 and 536 CE. Historical records suggest that the cooling occurred over approximately 5-7 years from one end to the other, mostly noted in southern Europe, eastern Mediterranean and eastward to China. North American tribes have no record of any major cold period around that time in the Northern Hemisphere temperatures but began dropping rapidly in 540 CE.
A 2015 study further supported the theory of a major eruption in "535 or early 536", with North American volcanoes considered a likely candidate.
The Gothic War began.
The Gothic War was a war fought in Italy and the adjoining regions of Dalmatia, Sardinia, Sicily and Corsica from 535 until 554 between the forces of the Eastern Roman Empire and the forces of the Ostrogothic Kingdom of Italy.
Theudebert I was the Merovingian king of Austrasia from 533 to his death in 548.
About this time according to natural evidence, a major volcanic eruption took place creating a 150-meter-thick cloud layer over the entire Earth, triggering a chain of climatic, agricultural, political and social changes that ushered in the Dark Ages.