Year 537 (DXXXVII) was a common year starting on Thursday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Second year after the Consulship of Belisarius (or, less frequently, year 1290 Ab urbe condita). The denomination 537 for this year has been used since the early medieval period, when the Anno Dominicalendar era became the prevalent method in Europe for naming years.
Vitiges sets up seven camps, overlooking the main gates and access routes to the city, in order to starve it out. He blocks the Roman aqueducts that are supplying Rome with water, necessary both for drinking and for operating the corn mills.[2]
April – The Goths capture the Portus Claudii at Ostia; the harbor is left unguarded by the Romans. Belisarius is forced to unload his supplies at Antium; he sends urgent messages for reinforcements to Constantinople.[4]
April 9 – Belisarius receives his promised reinforcements: 1,600 cavalry, mostly of Hunnic or Slavic origin and expert bowmen. Despite shortages, he starts raids against the Gothic camps and Vitiges is forced into a stalemate.[5]
June – In Rome, famine brings the city to despair; Belisarius sends his secretary Procopius to Naples for more reinforcements and supplies. Vitiges arranges a three-month armistice for Gothic envoys to travel to Constantinople.[6]
November – Belisarius brings his long-awaited reinforcements, namely 3,000 Isaurians and 1,800 cavalry embarked in Ostia, along with a supply convoy, safely to Rome. The Goths are forced to abandon the Portus Claudii.[7]
December – Belisarius sends John "the Sanguinary" with a force of 2,000 men towards Picenum, to plunder the east coast of Italy. He arrives at Ariminum (Rimini), where he is welcomed by the local Roman population.[8]
Eastern Wei sends an advance guard of three army columns through the Tong Pass, to attack Western Wei. The Western army under Yu-Wen Tai defeats one of the columns while the others retreat. Yu-Wen follows up, but runs into the main Eastern army (200,000 men). The Westerners are pushed back through the pass, and the Eastern army emerges from the mountains. Unexpectedly they are charged in the flank by 10,000 Western cavalry, and 6,000 Easterners are killed and 70,000 captured.[10]
John Cottistis starts a short-lived rebellion against Justinian I. He is declared emperor at Dara, but is killed four days later by conspiring soldiers.[11]