On its 70th anniversary, NATO is bigger than ever - here are its 29 members in action

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Soldiers from different countries during the opening ceremony of the 2018 NATO Summit at NATO headquarters in Brussels, Belgium, July 11, 2018.

• NATO's 12 founding members formed the transatlantic alliance in 1949.
• In the 70 years since, the organization has only grown, but it hasn't always been smooth.

On April 4, 1949 - almost exactly four years after Germany's unconditional surrender ended World War II in Europe - 12 countries signed the North Atlantic Treaty in Washington, DC.

Within five months, each of those countries had ratified the treaty, sealing their membership in the North Atlantic Treaty Organization, or NATO.

Read more: NATO held its largest war games since the Cold War in 2018 - one of more than 100 exercises it did last year

In the 70 years since, the alliance has responded to crises in Europe and around the world. It has also grown, incorporating Western European countries and former Soviet republics. NATO also counts countries in Asia, Oceania, and Latin America as global partners.

NATO's expansion hasn't been without growing pains, but the alliance, now in the process of accepting its 30th member, is bigger than ever.

You can see each country's forces in action, along with the date they joined NATO.