North Atlantic Treaty Organisation(NATO)

NATO is an Intergovernmental Military Alliance based on the North Atlantic Treaty which was signed on April 4,1949 in Washington D.C..The organisation constitutes a system of collective defence whereby its member states agree to mutual defense in response to an attack by any external party.
 The alliance includes 28 members in North America and Europe, with the newest being Albania and Croatia who joined in April 2009
NATO headquarters are in Brussels.
The treaty was created with an armed attack by the Soviet Union against Western Europe in mind, but the mutual self-defense clause was never invoked during the Cold War. Rather, it was invoked for the first time in 2001 in response to theSep 11,2001 attacks against the World Trade Center and The Pentagon in Operation Eagle Assist.
Founding Members of NATO that signed the treaty are -
1)Belgium
2)Canada
3)Denmark
4)France
5)Iceland
6)Italy
7)Luxembourg
8)Netherlands
9)Norway
10)Portugal
11)UK and
12)USA

Countries that signed the treaty and joined NATO are -

S No	Country	Year
1	Greece	1952
2	Turkey	1952
3	West Germany	1955
4	Spain	1982
5	Czech Republic	1999
6	Hungary	1999
7	Poland	1999
8	Bulgaria	2004
9	Estonia	2004
10	Latvia	2004
11	Lithuania	2004
12	Romania	2004
13	Slovakia	2004
14	Slovenia	2004
15	Abania	2009
16	Croatia	2009

NATO conducted their first military interventions inBosnia from 1991-95  and later Yugoslavia in 1999.
The Sep 11,2001 signalled the only occasion in NATO's history that Article 5 of the North Atlantic treaty has been invoked as an attack on all NATO members
Troops were deployed to Afghanistan under the NATO-led International Security Assistance Force(ISAF) by UNSC Resolution 1386 in Dec 2001
NATO Training Mission - Iraq was established in 2004 at the request of the Iraqi Interim Govt under the provisions of UNSC Resolution 1546
In March 2011 a multi-state coalition began a military intervention in Libya to implement UNSC Resolution 1973, which was taken in response to events during the Libyan Civil War and enforce a No-Fly Zone Over Libya