
There are many concerns that the missile explosion in Poland could constitute a violation of NATO Article 5 if it is found to be due to a Russian attack.
NATO's founding treaty in Article 5 focuses on collective defense, so if one member state is attacked, the rest come to its defense and the Alliance acts as a whole.
Article 5 was adopted at a time when the bloc was under threat of attack from the former Soviet Union.
"Collective defense means that an attack against one ally is considered an attack against all allies," this article states.
Article 5 has been activated only once by NATO since it was signed in 1949, the day after the September 11, 2001 terrorist attacks on the World Trade Center and Pentagon buildings in the US.
Meanwhile, Poland has recently declared that it is considering the activation of Article 4 of NATO, which provides that the parties will consult together and decide if their territorial integrity, political independence or security is under threat.
The 30 member states then initiate formal consultations at the request of the threatened member. The talks look at whether there is a threat and how to counter it, with decisions reached unanimously. However, Article 4 does not mean there will be action.
This consultation mechanism has been activated several times in the history of NATO. An example is a year ago, when Turkish soldiers were killed in an attack from Syria.
In that case, NATO decided to consult, but took no action.