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NATO responded to the Russian invasion of Ukraine by sending new troops to Eastern Europe and calling an emergency summit: Poland and the three Baltic republics – Estonia, Latvia and Lithuania – have appealed to Article 4 of the Atlantic Alliance Treaty, which provides for consultations between the 30 member states if one of them feels its territorial integrity, political independence or security threatened. Poland shares the border with Ukraine and Belarus, from where the offensive of Putin’s troops towards Kiev started; the Baltic republics, in addition to bordering Russia and Belarus, fear that the Kremlin could point towards the Baltic.
In this case, Article 5 would applyinvoked only once by the United States after 9/11, which provides military assistance from the entire NATO in case a member is attacked.

However, Article 4 was requested six times after the treaty was signed in Washington in 1949, of which four from Turkey: in 2003 for the war in Iraq; in June and October 2012, and then again in 2020, following Syrian assaults. NATO has sent military aid only twice. Latvia, Lithuania and Poland instead invoked it in 2014, after the Russian invasion of Crimea, and in November 2021, in response to the migrant crisis caused by Belarus on the Polish border. Today we held consultations under Article 4, the North Atlantic Council wrote in a statement. Our measures remain preventive, proportionate and gradual.