stronghold fortress of Vidin and its king Ivan Sratsimir by the Ottomans. 1397: The Kalmar Union is established, uniting Norway, Sweden and Denmark into one kingdom. 1397: Reign of Chimalpopoca begins as the third tlatoani of Tenochtitlan. Undated Transition from the Medieval Warm Period to the Little Ice Age. Crisis of the Late Middle Ages The poet Petrarch coins the term Dark Ages to describe the preceding 900 years in Europe, beginning with the fall of the Western Roman Empire in 476 through to the renewal embodied in the Renaissance. Beginning of the Ottoman Empire, early expansion into the Balkans. Iwan vault, Jamé Mosque of Isfahan, Isfahan, Iran, is built. Early 14th century: Kao Ninga paints Monk Sewing (attributed) in the Kamakura period (Cleveland Museum collection). An account of Buddha's life, translated earlier into Greek by Saint John of Damascus and widely circulated to Christians as the story of Barlaam and Josaphat, became so popular that the two were venerated as saints. Singapore emerges for the first time as an important fortified city and trading centre. Islam reaches Terengganu, on the Malay Peninsula as evidence by the Terengganu Inscription Stone. The Hausa found several city-states in the south of modern Niger. Work begins on the Great Enclosure at Great Zimbabwe, built of non-cemented, dressed stone. Research suggests the city's population to be between less than 10,000 to 18,000 at its peak. Inventions, discoveries, introductions Music of Ars nova Foundation of the University of Kraków Chinese text the Huolongjing by Jiao Yu describes fire lances, fire arrows (rockets), rocket launchers, land mines, naval mines, bombards, cannons, and hollow cast iron cannonballs filled with gunpowder, and their use to set ablaze enemy camps First pound lock in Europe reportedly built in Vreeswijk, Netherlands in 1373 References 2nd millennium Centuries