Europe

• The Vikings raid Dorestad
  Dorestad
  In the Early Middle Ages, Dorestad was the largest settlement of northwestern Europe. It was a large, flourishing trading place, three kilometers long, situated where the rivers Rhine and Lek diverge southeast of Utrecht in the Netherlands near the modern town of Wijk bij Duurstede...
  
  .
• Al-Andalus
  Al-Andalus
  Al-Andalus was the Arabic name given to a nation and territorial region also commonly referred to as Moorish Iberia. The name describes parts of the Iberian Peninsula and Septimania governed by Muslims , at various times in the period between 711 and 1492, although the territorial boundaries...
  
  : Second uprising of Toledo
  Toledo, Spain
  Toledo's Alcázar became renowned in the 19th and 20th centuries as a military academy. At the outbreak of the Spanish Civil War in 1936 its garrison was famously besieged by Republican forces.-Economy:...
  
   due to ethnic tensions in two years
  872
  Year 872 was a leap year starting on Tuesday of the Julian calendar.- Europe :* Battle of Hafrsfjord: Harald Fairhair becomes the first king of Norway....
  
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Asia

• A widespread failure of the agricultural harvest
  Harvest
  Harvest is the process of gathering mature crops from the fields. Reaping is the cutting of grain or pulse for harvest, typically using a scythe, sickle, or reaper...
  
   in Tang Dynasty
  Tang Dynasty
  The Tang Dynasty was an imperial dynasty of China preceded by the Sui Dynasty and followed by the Five Dynasties and Ten Kingdoms Period. It was founded by the Li family, who seized power during the decline and collapse of the Sui Empire...
  
   China
  China
  Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
  
   leads to a widespread famine
  Famine
  A famine is a widespread scarcity of food, caused by several factors including crop failure, overpopulation, or government policies. This phenomenon is usually accompanied or followed by regional malnutrition, starvation, epidemic, and increased mortality. Every continent in the world has...
  
  ; in the previous century the central government was able to curb famine with large grain stores
  Granary
  A granary is a storehouse for threshed grain or animal feed. In ancient or primitive granaries, pottery is the most common use of storage in these buildings. Granaries are often built above the ground to keep the stored food away from mice and other animals.-Early origins:From ancient times grain...
  
  , but this time the central government is already in decline and too weak to properly face the disaster.