The North Atlantic Treaty Organization, also called the (North) Atlantic Alliance, is an intergovernmental military alliance based on the North Atlantic Treaty which was signed on 4 April 1949. The organization constitutes a system of collective defence whereby its member states agree to mutual defense in response to an attack by any external party.
NATO
![NATO](https://freeyorkk.b-cdn.net/wp-content/uploads/2018/04/2000px-Flag_of_NATO.svg_-1150x863.png)