After WWII ended in 1945, Europe was both physically and ideologically fractured as nations sought to rebuild new divides and alliances began to develop.

Many new treaties and organizations were formed in the years that followed inlcuding 1949s North Atlantic Treaty, also known as NATO.

The treaty, initially signed by 12 nations, sought to defend its members from Soviet expansionism.

The Soviets were allied during WWII, were increasingly seen as a threat to democratic nations.

In response, NATO's article five was designed as a deterrent for attacks from adversaries like the USSR through the principle of collective defense, meaning an attack against one member is considered an attack against all.

Since then, NATO membership has grown to over 30 nations.

This expansion began in 1952, with Greece and Turkey strengthening the southeastern flank against the Soviets.

Then in 1955, West Germany joined NATO, while East Germany joined the Soviet dominated treaty known as the Warsaw Pact.

The next addition wouldn't occur until 1982, when Spain was allowed to join, and by 1990 Germany's membership was updated to include the entire region, reunifying East and West Germany.

Finally, in 1991, the Soviet Union dissolved, prompting many Warsaw Pact and post-Soviet era states to seek membership.

Despite the USSR no longer posing a threat.

In 1995, the Alliance published a study that showed the merits of continued NATO expansion, concluding that it would strengthen international security but only if new members fulfilled certain criteria.

Among other restrictions, new members must prove they have a functioning democratic political system, treat minority populations fairly, and possess the ability and willingness to contribute militarily.

But these stipulations are just one part of the screening interview.

The real approval process outlined in article ten has two main hurdles.

First, only European nations are eligible.

And second, there must be unanimous agreement from all existing members, which is easier said than done.

Despite these barriers to entering their lines fully, NATO has a much broader influence than it might seem on the surface, with more than 40 nonmember countries and various international organizations partnering with the alliance.

While the Cold War has long been over, NATO is still a massively influential alliance and one that continues to shape the future of democracy and peace across the world.

Simple Civics.

Brought to you in part by the Indiana State Teachers Association.