Headquartered in Brussels, Belgium, NATO was founded in 1949 by a collection of twelve world powers including the United States, United Kingdom, France, Italy and Canada. It expanded in 1952 to include Greece and Turkey and then, again, in 1955 to formally introduce West Germany. 1982 saw Spain come aboard and the Czech Republic, Hungary and Poland followed in a 1999 expansion. March 2004 introduced members Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia and Slovenia until, finally, in 2009 Albania and Croatia were welcomed. Formed to counter the threat of Soviet expansion in Europe, NATO resides today as an impressive collective military power (at least on paper) with the capability to call nearly 3.5 million personnel into service and expenditures totaling over $900 million (USD) with the United States taking both the material and financial lead.
There are a total of (26) countries of the European Union represented in the GFP database. While there are officially twenty-eight total NATO members, Iceland and Luxembourg are not included in this list due to unmet conditions and minimums. Iceland does not officially maintain a standing army.
Sources: CIA.gov, CIA World Factbook, wikipedia.com, public domain print and media sources and user contributions. Some values may be estimated when official sources are lacking.