https://www.nato.int/cps/en/natohq/topics_49187.htm

Since the Alliance’s creation in 1949, Article 4 has been invoked seven times:

1. On 10 February 2003, Türkiye formally invoked Article 4, asking for consultations in the NAC on defensive assistance from NATO in the event of a threat to its population or territory resulting from armed conflict in neighbouring Iraq. NATO agreed a package of defensive measures and conducted Operation Display Deterrence from the end of February to early May 2003.
2. On 22 June 2012, Türkiye requested a NAC meeting under Article 4 after one of its fighter jets was shot down by Syrian air defence forces.
3. On 3 October 2012, Türkiye requested Article 4 NAC consultations when five Turkish civilians were killed by Syrian shells. Following these incidents, on 21 November 2012, Türkiye requested the deployment of Patriot missiles. NATO agreed to this defensive measure to help Türkiye defend its population and territory, and to help de-escalate the crisis along the border.
4. On 3 March 2014, Poland invoked Article 4 following increasing tensions in neighbouring Ukraine, as a result of Russia’s aggressive actions.
5. On 26 July 2015, Türkiye requested that the NAC convene in view of the seriousness of the situation following terrorist attacks, and to inform Allies of the measures it was taking.
6. On 28 February 2020, Türkiye requested consultations following the death of Turkish soldiers in air strikes by the Syrian regime and its backer Russia in Idlib province.
7. On 24 February 2022, Bulgaria, Czechia, Estonia, Latvia, Lithuania, Poland, Romania and Slovakia requested to hold consultations under Article 4 following Russia’s full-scale invasion of Ukraine.