Explanation:

• The North Atlantic Treaty Organization (NATO) has organised three-part series of multilateral military exercises, dubbed as Steadfast Defender 2021, to test NATO’s readiness and military mobility.
• The exercise will be taking place in the Atlantic and Europe, and into the Black Sea region. 

• Aim of the exercise 

• Ensure that NATO troops are well-trained, and are able to operate together and ready to respond to any threat from any direction.
• Demonstrate the value of North America and Europe working together to keep their nations safe in a more challenging security environment.
• Enhance interoperability and military capabilities on air, land, and sea among NATO members.

• NATO

• North Atlantic Treaty Organization (NATO), military alliance established by the North Atlantic Treaty (also called the Washington Treaty) of April 4, 1949, which sought to create a counterweight to Soviet armies stationed in central and eastern Europe after World War II. 

• Members -

• ALBANIA (2009)
• BELGIUM (1949)
• BULGARIA (2004)
• CANADA (1949)
• CROATIA (2009)
• CZECH REPUBLIC (1999)
• DENMARK (1949)
• ESTONIA (2004)
• FRANCE (1949)
• GERMANY (1955)
• GREECE (1952)
• HUNGARY (1999)
• ICELAND (1949)
• ITALY (1949)
• LATVIA (2004)
• LITHUANIA (2004)
• LUXEMBOURG (1949)
• MONTENEGRO (2017)
• NETHERLANDS (1949)
• NORTH MACEDONIA (2020)
• NORWAY (1949)
• POLAND (1999)
• PORTUGAL (1949)
• ROMANIA (2004)
• SLOVAKIA (2004)
• SLOVENIA (2004)
• SPAIN (1982)
• TURKEY (1952)
• THE UNITED KINGDOM (1949)
• THE UNITED STATES (1949)