The North Atlantic Treaty Organization (NATO) was founded in 1949 as an initiative to provide collective security against the Soviet Union and stop Soviet expansionism. The alliance founders were the United States, Canada, the United Kingdom, Belgium, Denmark, France, Iceland, Italy, Luxembourg, Norway, Portugal, and the Netherlands, which signed the North Atlantic Treaty on April 4, 1949. The most important part of the Treaty is the famous Article 5, which provides that an attack on any NATO member in Europe or North America “shall be considered an attack against them all” and following such an attack, each member state would take “such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area.” However, Article 5 has been invoked just once in history, after attacks on the US on September 11, 2001, when the alliance launched several air and maritime operations to prevent the movement of terrorists and weapons of mass destruction. Since 1949, NATO has expanded significantly through several rounds of enlargement, bringing the total number of member states from 12 to 30 until 2020.

Relations between NATO and Russia were established after the end of the Cold War in 1991 and since then the two parties signed numerous cooperation agreements and created the NATO-Russia Council. However, these relations deteriorated severely in 2014, when NATO suspended all practical cooperation after the Russian annexation of Crimea. Nevertheless, relations between the two sides reached their lowest point in 2022 when Russia launched a full-scale invasion of Ukraine.

Following the outbreak of war in Ukraine, Finland and Sweden felt threatened, as they share a border with Russia, which prompted them to abandon their decades-long stance of military neutrality and formally request NATO membership. After completion of the official procedure, Finland joined NATO in April 2023 as the 31st member, while Sweden received the green light in February 2024, becoming the 32nd member of the alliance. With the accession of these two Nordic countries, the Russian border with NATO more than doubled and the Baltic Sea, a strategically important region for Moscow both from a military and economic point of view, has become what some have called a "NATO lake". Since this latest expansion of the alliance, Russian President Vladimir Putin's rhetoric has become more threatening, as he said that an attack on Russia would have "tragic consequences" and that Russia owns more powerful weapons than NATO.