Which of the following statement(s) is/are correct about ‘North Atlantic Treaty Organisation’?
1. It is an intergovernmental military alliance based on the ‘Washington Treaty’ signed in the year 1949.
2. As of now, the collective defence of the NATO members apply to the military attacks in land, sea or in the air only.
3. The headquarters of NATO is located in Washington DC.
4. The Article 5 of the NATO Charter has been invoked only once which is the treaty provision whereby any member of the alliance invites the participation of all treaty members in its war against an external party.
Select the correct codes from below -