Estonia was conquered by crusaders from Denmark and Germany during the 13th century. The new rulers imposed taxes and duties, and gradually reduced parts of the indigenous population to serfs. Oppression hardened as the new masters built manor-houses all over the country. The area was also politically unstable. The Northern Estonian provinces of Harria (Harju) and Vironia (Viru) were given to Denmark, however the Danish power remained weak. The Danish vassals were mostly German-speaking settlers, however some were also indigenous Estonian-speakers.
On St. George's Night (April 23) 1343, Estonians in Harria started a large uprising. They renounced Christianity, and killed mercilessly everybody with German ancestry (chronicles give 1,800 as the total number of victims). It was mostly a peasant uprising, but ethnic Estonian vassals probably took part in it. Insurgents conquered the Cistercian monastery-fortress in Padise and tried to besiege Reval (Tallinn), the provincial capital, which they promised to hand over to the their ally, the king of Sweden. The provinces of Wiek (Läänemaa) and Oesel (Saaremaa) joined the insurgency.
Insurgents elected their own leaders who were called "kings" in German chronicles. The four insurgent "kings" arrived as truce envoys to negotiate with the Livonian Order. The Estonian "king" offered to obey the master of Livonia provided they had no overlords over them; but the master wanted to know why they had killed so many people, including 28 monks of Padise. The answer was that any German deserves to be killed even if he were only two feet tall. The master of the order Burchard von Dreileben did not like the answer and all four Estonian "kings" were hanged in the castle of Weissenstein (Paide) in the province of Jerwia (Järva). The chronicle blames the incident on the envoys themselves, saying they had promised to kill all Germans and tried to kill the Master of Order. Many historians dismiss the explanation and say the negotiations were just a ruse to kill the leaders of the insurgency.
On May 14th, the leaderless insurgents of Harria lost the battle of Kanavere against the Order troops. The Estonian leaders were killed. Four days later arrived the Estonian allies, Swedish-Finnish troops led by Dan Nilsson, the bailiff of Åbo; but it was too late. They were received by the commander of the Livonian Order who convinced them to keep the truce.
The chronicler Bartholomäus Hoeneke also tells a story about Estonians making a scheme to get inside the castle of Fellin (Viljandi), hiding armed warriors in bags of grain. The plot failed when one mother tipped the Order commander about the plot, in exchange of the life of her son. That is obviously unhistorical legend but has inspired several writers.
The rebellion on the island of Oesel lasted two years. The Oeselian "king" Vesse was put to death in 1344. The insurgencies in Oesel were stifled in 1345. After the rebellion Denmark sold its domains in Estonia to the Teutonic Order in 1346.
The St. George’s Night Uprising has inspired several historical novels by Estonian writers, such as Eduard Bornhöhe's "The Avenger". Soviet Union tried to use the anniversary of the uprising in 1943 to pit the Estonians against the Germans.
The uprising is also a popular subject of debates among Estonian historians and literati. Some, like Edgar V. Saks and the writer Uku Masing have argued, basing on contemporary documents, that, contrary to claims in the chronicles, the uprising was not a fight against the Christianity but only against the Livonian Order and the crimes committed attributed to this "uprising" are actually committed by the Order. Some see it as a continuation between struggle between the Order and the Holy See. Others dismiss such claims as biased and unhistorical.