Prince of Novgorod (1236–1240; 1241–1256; 1258–1259)
In 1236, Alexander was appointed by the Novgorod Republic as the prince of Novgorod (knyaz), where he had already served as his father's governor. He was chosen for the position by his father, but the decision was approved by the veche, which needed his armies. The Novgorod chronicle describes how Yaroslav left his son, Alexander, in Novgorod and took with him "senior Novgorodians" and a hundred men from Torzhok and "sat in Kiev upon the throne". When his father was called away in 1238 because of a Mongol invasion of Northeastern Russia, Alexander began to rule on his own.
In the Battle of the Sit River (1238), in which the Mongols effectively conquered the Grand Principality of Vladimir, the reigning prince Yuri II of Vladimir was killed. His younger brother, Yaroslav II of Vladimir (Alexander's father), requested and received from the Mongol khan his permission to become the new prince. As prince, he assigned Novgorod to his son Alexander.
Alexander continued to enforce the anti-Western views of his family, which made him unpopular among the veche.
In 1240, three years after obtaining papal authorization, the Swedes launched the Second Swedish Crusade in the easternmost part of the Baltic region. The Finnish mission's eastward expansion led to a clash between Sweden and the city-state of the Novgorod Republic, since the Karelians had been allies and tributaries of Novgorod since the mid-12th century. The Swedish army was led by Birger Jarl and consisted of Norwegians and Finnish tribes. After a successful campaign into Tavastia, the Swedes advanced further east. According to Russian sources, the Swedish army landed at the confluence of the rivers Izhora and Neva in northwestern Russia, when Alexander and his small army suddenly attacked the Swedes on 15 July 1240 and defeated them in the Battle of the Neva.
The battle is not mentioned in any Swedish sources; all accounts of the battle are from two Russian sources, which are largely inadequate. Although some Russian sources written centuries later describe its as a very large battle, it is not clear if it was a huge battle or just part of periodic clashes between Sweden and Novgorod that was exaggerated for political purposes. Soviet-era historian Igor Pavlovich Shaskol'skii suggested that the attack was coordinated, referring to the Life of Alexander Nevsky, the only Russian source besides the First Novgorod Chronicle that mentions the battle, in which it is stated that the Swedes intended to conquer Novgorod. However, according to John Lister Illingworth Fennell: "there is no evidence of any coordination of action between the Swedes, the Germans and the Danes, nor is there anything to show that this was more than a continuation of the Russo-Swedish conflict for mastery over Finland and Karelia".
The event was later depicted as being of national importance, and in the 15th century, Alexander received the sobriquet Nevsky ("of the Neva").
In the September 1240 Izborsk and Pskov campaign, troops of the Bishopric of Dorpat, the Livonian Order, and the exiled pretender-prince Yaroslav of Pskov overthrew the pro-Suzdal faction which supported Alexander.
In late 1240 or early 1241, fearing the undue influence of Alexander over the veche and amid fears of him becoming a sole ruler, the Novgorodians banished Alexander to Pereslavl-Zalessky.
In the winter 1240–1241 Votia campaign, the Bishopric of Ösel–Wiek, the Livonian Order, as well as Estonians (Chud') with support from local Votian leaders attacked Votia. It is unclear whether or not Votia was a tributary of Novgorod at this time. According to Anti Selart, the allies likely only intended to acquire pagan lands and convert them to Catholicism, rather than attacking Novgorod, which was already Christianized. On the other hand, the campaign was "a purely political undertaking which had nothing to do with conversion of pagans". Although the Northern Crusades were aimed at pagan Balts and Baltic Finnic peoples, rather than Orthodox Russians, several unsuccessful attempts were made to persuade Novgorod to convert to Catholicism, which were resisted by Alexander.
The Novgorodian authorities recalled Alexander, and in the spring of 1241, he returned from exile and assembled an army. Alexander conquered Pskov and Koporye from the crusaders, executing the Votians that cooperated with the invaders. He then continued into Estonian-German territory. The crusaders defeated a detachment of the Novgorodian army. As a result, Alexander set up a position at Lake Peipus. On 5 April 1242, in the Battle on the Ice, Alexander and his men faced the Livonian heavy cavalry led by Hermann of Dorpat, brother of Albert of Buxhoeveden. Alexander's army defeated the enemy, halting the eastward expansion of the Teutonic Order. Later in 1242, the Germans agreed to relinquish control of any Russian territory still occupied and to exchange prisoners of war. Later Russian sources elevated the importance of the battle and portray it as one of the great Russian victories of the Middle Ages.
The Livonian Rhymed Chronicle narrates the events of the battle:
There is a city in Russia called Novgorod, and when its king [Alexandre] heard what had happened he marched towards Pskov with many troops. He arrived there with a mighty force of many Russians to free the Pskovians and these latter heartily rejoiced. When he saw the Germans he did not hesitate long. They drove away the two Brothers, removed them from their governorship and routed their troops. The Germans fled and allowed the land to revert to the Russians. Thus it went for the Teutonic Knights, but if Pskov had been protected it would have benefited Christianity until the end of the world. It is a mistake to take a fair land and fail to occupy it properly. It is deplorable, for the result is sure to be disastrous. The king of Novgorod then returned home.
A Soviet evaluation presented Alexander's victories as having "saved the Russian people from sharing the fate of the Baltic tribes and the Slavs of the Elbe who were enslaved by the Germans". Igor Shaskovsky called the offensive the largest during the feudal period. On the other hand, historians like Fennell have doubted that this victory was a turning point in Russian history. He notes that the chronicle of Suzdal downplays the event to the point that Alexander's brother Andrey is seen as the hero.
After the Livonian invasion, Nevsky continued to strengthen the Republic of Novgorod. He sent envoys to Norway and, as a result, a first peace treaty between Novgorod and Norway was signed in 1251. Alexander defeated the Swedes in Finland after they made another attempt to block the Baltic Sea from the Novgorodians in 1256. In 1261, Alexander also made a treaty with Lithuanian king Mindaugas against the Livonian Order, but the planned attack failed as Alexander was summoned to Sarai by the khan.
