Peter 1 carried out his reforms without thinking through and systematizing them in advance. All changes occurred between various military concerns and campaigns. There was no exception to the period when the Great Northern War was on.
The military operations against Sweden required enormous exertion of the forces of the entire state. That is why the entire Northern War under Peter 1, was accompanied by activities within the country. All internal changes were aimed at meeting military needs.
The Northern War required well-trained officers and soldiers. In this regard, a military reform was carried out. Military schools were created, “Military Articles” and “Company ranks” (new charters) were published, and a fleet was organized.
The Northern War also required cash. Peter 1 introduces a capitation tax, new taxes. Affected reforms and the industrial sector. The Northern War required uniforms, provisions, and weapons. All the reforms carried out allowed to improve the supply of the army, to begin the construction of fortresses.
In 1700, on August 22, the Russian army set off on a campaign to the Swedish fortress. By autumn, Narva was besieged. However, the siege was not entirely successful. The stock of gunpowder and cores was only for fourteen days. For the most part, the regiments were led by foreign officers who were very careless about their duties. In 1700, in November, the Swedes suddenly attacked Russian positions, taking the army to flight. At the same time, two regiments (Semenovsky and Preobrazhensky), preserving the battle order, fought off the attackers, covering the flight of the entire army.
The Swedish king decided that the Russians were defeated, and sent his forces against Poland. While Charles 12 made his Polish campaigns, Peter 1 was actively engaged in the reconstruction and reform of the army. New sets of soldiers began in the newly formed regiments, the training of Russian officers. More than 300 guns were cast during the year. Partly casting was carried out from the removed bells from the church belfries.
Peter's activity soon yielded results. In 1702, the Russian army captured Noteburg (ancient Oreshek) in the autumn, and another Swedish fortress Nyenschanz was captured in the spring, not far from which the Peter and Paul Fortress was laid. Tarta (Derpt) and Narva fell in 1704.
At this time, Charles 12, after the defeat of Saxony and Poland, forces the Polish ruler Augustus 2 to abandon his throne and alliance with Russia. Thus, Peter 1 was left without allies.
Rested after the conquest of Saxony, the army of Swedes at the end of 1707 went to Russia. The Swedes in December this year took Grodno, Mogilev. An urgent strengthening of Moscow began on the orders of Peter. Before capturing the city, Karl was going to connect with the Levengaupt corps that had left him from Riga. The corps came with stocks of weapons and food. However, in 1708, in September, the Russian army defeated Swedish reinforcements, seizing food and weapons. As a result of this battle near the village of Lesnoy, only about 7 thousand half-naked and half-starved soldiers from the 16 thousandth corps came to Karl.
After this failure, the Swedish king had high hopes for Ukraine. Hetman Mazepa, betraying the Russian state, in 1708 joined the Swedes. However, only 2 thousand soldiers brought Mazepa with him - Ukraine remained faithful to Russia, moreover, Ukrainian peasants began a popular movement against the Swedish troops .
Near Poltava there was a decisive battle. In 1709, on June 27, the Swedes suffered an absolute defeat. The defeated troops fled to the Dnieper, to the south, where their remains were captured by the Menshikov corps. Mazepa, the Swedish king, several hundred Cossacks and Swedes fled to Turkey.
After 1709, the military power of Sweden was broken. The Northern War contributed to the fact that Russia became the most powerful power in Northern Europe.
In 1721, on August 30, peace was concluded between Sweden and Russia. Under the agreement, Finland was returned to the Swedish side, while Russia received Karelia, Estonia, Livonia, Ingria. The Senate presented the imperial title to Peter, the title of "Great" and "Father of the Fatherland" in commemoration of the victory. From that moment, Russia began to be called the Empire.