Who Are the Leaders of NATO? Here's a Closer Look at the Organization

President Donald Trump made headlines on Wednesday for his criticism of allies in the North Atlantic Treaty Organization (NATO) during a summit in Brussels.

The president has criticized member states for not paying enough for the protections they receive from the U.S. as a part of the organization. He added that all nations must increase their contributions from 2 percent of their gross domestic product to 4 percent.

Trump also criticized Germany on Wednesday, saying the European nation is "totally controlled" by Russia and is becoming a "captive," citing an oil deal between Berlin and Moscow

To better understand NATO, here's a closer look at the organization—including its leaders and member countries.

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President Donald Trump reaches out to British Prime Minister Theresa May at the 2018 NATO Summit on July 11, 2018, in Brussels. Jasper Juinen/Getty Images

What countries are part of NATO?

Twelve nations founded NATO in 1949: Belgium, Canada, Denmark, France, Iceland, Italy, Luxembourg, Netherlands, Norway, Portugal, United Kingdom and the United States. The alliance has since grown to 29 members, with Montenegro being the most recent to join in 2017.

Who heads NATO?

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NATO Secretary General Jens Stoltenberg speaks to reporters at the 2018 NATO Summit at NATO headquarters on July 11, 2018 in Brussels, Belgium Sean Gallup/Getty Images

NATO Secretary-General Jen Stoltenberg, a national of Norway, has led the international alliance since October 2014. He previously served as the prime minister of his country from 2005 to 2013.

Who are NATO's international leaders?

U.S.

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U.S. President Donald Trump speaks to reporters on the South Lawn before boarding Marine One and departing the White House, on July 9, 2018 in Washington, DC Al Drago/Getty Images

President since January 2017, Donald Trump serves as the head of state and head of government, making him the top national leader to represent the U.S. in the NATO alliance.

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Former Sen. Kay Bailey Hutchison (R-TX) testifies during her confirmation hearing to be United States permanent representative on the Council of the North Atlantic Treaty Organization, during a Senate Foreign Relations Committee hearing on Capitol Hill, June 20, 2017 in Washington, DC Mark Wilson/Getty Images

Kay Bailey Hutchison, a former Republican senator from Texas, became the U.S. ambassador to NATO in August 2017. Speaking to reporters at the summit, Hutchison said, "The major thing, the major deliverable, the major overall theme of this summit is going to be NATO's strength and unity."

United Kingdom

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German chancellor Angela Merkel, Prime Minister Theresa May and Polish Prime Minister Mateusz Morawiecki attend a press conference during the second day of Western Balkans summit at Lancaster House on July 10, 2018 in London, England Stefan Rousseau - WPA Pool/Getty Images

British Prime Minister Theresa May took office in July 2016. Although the Queen of England is technically the head of state for the United Kingdom, the prime minister leads political and state affairs, including relations with NATO. Taking aim at recent resignations that racked May's government this week, Trump said on Tuesday that the U.K. is "in somewhat turmoil," suggesting a planned meeting with Russian President Vladimir Putin will be his easiest during his Europe trip.

Germany

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German Chancellor Angela Merkel (CDU) arrives for the weekly cabinet meeting in the German Chancellory on July 11, 2018 in Berlin, Germany Michele Tantussi/Getty Images

Chancellor Angela Merkel has led Germany since she rose to power in 2005. Merkel defended her country against Trump's criticism on Wednesday, "I have experienced myself how a part of Germany was controlled by the Soviet Union. I am very happy that today we are united in freedom ... because of that we can say that we can make our independent policies and make independent decisions," she said.

France

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French President Emmanuel Macron holds a press conference on the final day of the European Council leaders' summit on June 29, 2018 in Brussels, Belgium Jack Taylor/Getty Images

Emmanuel Macron became president of France in May 2017. Tensions between France and the U.S. have increased significantly in recent weeks, as Trump's trade war has escalated. At the Group of Seven (G-7) summit in Canada last month, Macron said France and the other wealthy nations would be just fine without support from the U.S.

Canada

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Canadian Prime Minister Justin Trudeau (L) and Canadian Defense Minister Harjit Sajjan arrive at the 2018 NATO Summit at NATO headquarters on July 11, 2018 in Brussels, Belgium Sean Gallup/Getty Images

Justin Trudeau has led his country since he became prime minister in 2015. At the summit, Trudeau has defied Trump's demands to increase military spending, moving instead to decrease funding.

Turkey

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U.S. President Donald Trump (L) and Turkish President Recep Tayyip Erdogan attend the opening ceremony at the 2018 NATO Summit at NATO headquarters on July 11, 2018 in Brussels, Belgium Sean Gallup/Getty Images

President Recep Tayyip Erdoğan has led Turkey as president since 2014. Prior to that, he served as prime minister of the country from 2003 to 2014. He recently won re-election, at which time he gained sweeping new powers that came after constitutional changes made during his previous term.

Norway

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Norway's Prime Minister Erna Solberg (L) shakes hands with NATO Secretary General Jens Stoltenberg (R) during the NATO summit, at the NATO headquarters in Brussels, on July 11, 2018 DENIS CHARLET/AFP/Getty Images

Erna Solberg assumed office as Norway's prime minister in 2013. Her country has seen increased tensions with Russia in recent months, as her administration has asked the U.S. to significantly increase the number of troops it stations in the country. Russia sees the move as a provocation, due to its proximity to Norway.

Poland

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Poland President Andrzej Duda (L) shakes hands with NATO Secretary General Jens Stoltenberg (R) during the NATO (North Atlantic Treaty Organization) summit, at the NATO headquarters in Brussels, on July 11, 2018 DENIS CHARLET/AFP/Getty Images

Polish President Andrzej Duda has held office since 2015. His right-wing government has drawn criticism from other European leaders. At the same time, Poland has increasing concerns about Russia's expansionist ambitions and has reportedly offered $2 billion for the U.S. to be stationed permanently within its borders.

Belgium

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Belgian Prime Minister Charles Michel (L) is welcomed by NATO Secretary General Jens Stoltenberg (R) as he arrives for the NATO summit, at the NATO headquarters in Brussels, on July 11, 2018. ERIC LALMAND/AFP/Getty Images

Charles Michel has been the prime minister of Belgium since 2014. Belgium hosted the NATO summit at the organization's headquarters in Brussels.

Albania

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Prime Minister of Albania Edi Rama (L) shakes hands with NATO Secretary General Jens Stoltenberg (R) during the NATO summit, at the NATO headquarters in Brussels, on July 11, 2018 DENIS CHARLET/AFP/Getty Images

Edi Rama has been the prime minister of Albania since 2013.

Bulgaria

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Bulgaria President Rumen Radev (L) shakes hands with NATO Secretary General Jens Stoltenberg (R) during the NATO summit, at the NATO headquarters in Brussels, on July 11, 2018 DENIS CHARLET/AFP/Getty Images

Rumen Radev became president of Bulgaria in 2017.

Croatia

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Croatia's President Kolinda Grabar-Kitarovic arrives to attend the NATO summit, in Brussels, on July 11, 2018 ERIC LALMAND/AFP/Getty Images

Kolinda Grabar-Kitarovic became president of Croatia in 2015.

Czech Republic

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French President Emmanuel Macron (L) speaks with Czech Republic President Milos Zeman after arriving to attend the North Atlantic Council meeting during the NATO summit, at the NATO headquarters in Brussels, on July 11, 2018 EMMANUEL DUNAND/AFP/Getty Images

Milos Zeman assumed office as president of his country in 2013.

Denmark

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Denmark's Prime Minister Lars Lokke Rasmussen (R) arrives to attend the NATO summit, in Brussels, on July 11, 2018 DENIS CHARLET/AFP/Getty Images

Lars Lokke Rasmussen took office as prime minister of Denmark in 2015.

Estonia

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Estonia's Prime Minister Juri Ratas (L) shakes hands with NATO Secretary General Jens Stoltenberg (R) during the NATO summit, at the NATO headquarters in Brussels, on July 11, 2018 DENIS CHARLET/AFP/Getty Images

Juri Ratas took office as prime minister of Estonia in 2016.

Greece

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Greece Prime Minister Alexis Tsipras (L) is welcomed by NATO Secretary General Jens Stoltenberg (R) as he arrives for the NATO summit, at the NATO headquarters in Brussels, on July 11, 2018 ERIC LALMAND/AFP/Getty Images

Alexis Tsipras assumed office as prime minister of Greece in 2015.

Hungary

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Hungarian Prime Minister Viktor Orban arrives for the NATO (North Atlantic Treaty Organization) summit, at the NATO headquarters in Brussels, on July 11, 2018 FRANCOIS MORI/AFP/Getty Images

Prime Minister Viktor Orban has held the position in Hungary since 2010.

Iceland

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Iceland Prime Minister Katrin Jakobsdottir (L) speaks with NATO Secretary General Jens Stoltenberg (R) during the NATO summit, at the NATO headquarters in Brussels, on July 11, 2018 DENIS CHARLET/AFP/Getty Images

Katrin Jakobsdottir assumed office as prime minister of Iceland in 2017.

Italy

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Italy's Prime Minister Giuseppe Conte (C) and Italy's Minister for Foreign Affairs Enzo Moavero Milanesi (R) arrive to attend the NATO summit, in Brussels, on July 11, 2018 DENIS CHARLET/AFP/Getty Images

Giuseppe Conte became prime minister of Italy in June.

Latvia

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Latvia's President Raimonds Vejonis speaks to journalists as he arrives to attend the NATO summit, in Brussels, on July 11, 2018 DENIS CHARLET/AFP/Getty Images

Raimonds Vejonis assumed office as president in 2015.

Lithuania

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Lithuania President Dalia Grybauskaite (L) is welcomed by NATO Secretary General Jens Stoltenberg (R) as she arrives for the NATO summit, at the NATO headquarters in Brussels, on July 11, 2018 ERIC LALMAND/AFP/Getty Images

Dalia Grybauskaite has been president of Lithuania since 2009.

Luxembourg

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Luxembourg's Prime Minister Xavier Bettel (C) arrives with Luxembourg's Defence Minister Etienne Schneider (L) to attend the NATO summit, in Brussels, on July 11, 2018 DENIS CHARLET/AFP/Getty Images

Xavier Bettel became prime minister of Luxembourg in 2013.

Montenegro

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Montenegro President Milo Dukanovic (L) arrives to attend the NATO summit in Brussels, on July 11, 2018 ERIC LALMAND/AFP/Getty Images

Milo Dukanovic took office as president of Montenegro in May.

Netherlands

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Netherland's Prime Minister Mark Rutte waves as he arrives to attend the NATO summit in Brussels, on July 11, 2018 ERIC LALMAND/AFP/Getty Images

Mark Rutte has been prime minister of the Netherlands since 2010.

Portugal

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Portugal's Prime Minister Antonio Costa (L) arrives to attend the NATO summit, in Brussels, on July 11, 2018 DENIS CHARLET/AFP/Getty Images

Antonio Costa assumed office as prime minister of Portugal in 2015.

Romania

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Romania's President Klaus Werner Iohannis answers journalists' questions as he arrives to attend the NATO summit, in Brussels, on July 11, 2018 DENIS CHARLET/AFP/Getty Images

Klaus Werner Iohannis became president of Romania in 2014.

Slovak Republic

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Slovak Republic's President Andrej Kiska (L) arrives to attend the NATO summit, in Brussels, on July 11, 2018 DENIS CHARLET/AFP/Getty Images

Andrej Kiska has been president of the Slovak Republic since 2014.

Slovenia

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Slovenia Prime Minister Miro Cerar (L) shakes hands with NATO Secretary General Jens Stoltenberg (R) during the NATO summit, at the NATO headquarters in Brussels, on July 11, 2018 DENIS CHARLET/AFP/Getty Images

Miro Cerar became his country's prime minister in 2014.

Spain

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Spain's Prime Minister Pedro Sanchez (R) speaks with US President Donald Trump after arriving to attend the North Atlantic Council meeting during the NATO summit, at the NATO headquarters in Brussels, on July 11, 2018 EMMANUEL DUNAND/AFP/Getty Images

Pedro Sanchez became Spain's prime minister in June.

Who Are the Leaders of NATO? Here's a Closer Look at the Organization | World