NATO member states Poland, Estonia, Latvia and Lithuania have on Thursday triggered NATO Article 4 to launch consultations within the alliance over Russia's attack on Ukraine. Article 4 of The North Atlantic Treaty says: "The Parties will consult together whenever, in the opinion of any of them, the territorial integrity, political independence or security of any of the Parties is threatened," According to the NATO website, consultation under Article 4 can result in collective action among the 30 member states. Article 4 has previously been invoked six times since the alliance initiated in 1949, most recently by Turkey in February 2020 after dozens of Turkish soldiers were killed due to an attack by Syrian government forces in opposition-held areas of northern Syria, the NATO website says. Turkey has invoked Article 4 on four other occasions; once in 2015 to inform the alliance of its response to terrorist attacks in the country; twice in 2012 after a Turkish warplane was shot down in northern Syria and after Turkish civilians were killed by Syrian shelling; and third in 2003 when it asked for alliance help to protect its population from any spillover from the war in neighbouring Iraq. On two of those occasions, NATO had responded with military aid, sending Patriot missile batteries to protect against Syrian attacks in 2012 as well as aircraft and missile batteries to southeastern Turkey along the border with Iraq in 2003. Poland also invoked Article 4 in 2014 after previous Russian aggression in Ukraine, a meeting that led to further alliance efforts to stand together against any threats. Article 4 is separate from Article 5, which is the NATO's declaration that an attack against one member is considered an attack against all.
