Since the beginning of the history of humanity nations established alliances with others to protect temselves from the third parties. There were several great alliances in the history and the most memorable could be the alliances during the WWII. What about current alliances bewteen nations. According to Wikipedia, this is the situation;

Current military-security alliances

Continental

Africa

•  African Union – All 55 African nations are members

Economic Community of Central African States          

• • Council for Peace and Security in Central Africa (COPAX)
• Economic Community of West African States               
  • ECOMIL
  • ECOMOG

Asia

• Axis of Resistance   
•  Organization of the Eurasian Law Enforcement Agencies with Military Status (TAKM) is a cooperation organization of Turkey, Azerbaijan, Mongolia, and Kyrgyzstan.
•  Peninsula Shield Force The military force of the Persian Gulf.      
• Shanghai Cooperation Organisation (SCO)        

Europe

•   Anglo-Portuguese Alliance, originally signed in 1373, is the oldest alliance still in force in the world.
•    BALTRON is a joint Estonian—Latvian—Lithuanian Naval Squadron.
•   Entente Cordiale / Defence and Security Co-operation Treaty is a joint Military alliance between France and the United Kingdom.
•   Franco-German Brigade is a joint French-German Brigade.
•  The European Union maintains a Common Security and Defence Policy, including a mutual defence clause
•  GUAM (Georgia, Ukraine, Azerbaijan and Moldova) cooperates on “international and regional security” and maintains a joint peacekeeping force.

North America

•   North American Aerospace Defense Command (NORAD)

Oceania

•   ANZAC is a joint military alliance between Australia and New Zealand.

South America

•  Union of South American Nations – Includes Venezuela, Uruguay, Bolivia, Guyana and Suriname, with Peru being a suspended member of UNASUR.
  • South American Defense Council (SADC)^[1]      
• Forum for the Progress and Development of South America (PROSUR) – currently being reformed to replace the Union of South American Nations.        

Intercontinental

Africa and Asia

•  Arab League                      

• Islamic Military Alliance (IMAFT), a 34-member alliance based at a joint command center in Riyadh, Saudi Arabia. Its creation was first announced by Mohammad bin Salman Al Saud, the Saudi Minister of Defense, on December 14, 2015.                                   

Africa and South America

• South Atlantic Peace and Cooperation Zone (ZPCAS)                        

Americas

• Organization of American States Includes all 35 nations in the Americas, although Venezuela has elected to withdraw and Cuba has chosen not to resume participation.
  • Inter-American Defense Board
• Rio Pact                  

Eurasia

•  Collective Security Treaty Organization, Military alliance with 6 former Soviet republics: Armenia, Belarus, Kazakhstan, Kyrgyzstan, Russia and Tajikistan.      
• Union State is an alliance between Russia and Belarus  
• Agreement on Strategic Partnership and Mutual Support an alliance between Turkey and Azerbaijan  
• 2001 Sino-Russian Treaty of Friendship a twenty-year treaty between China and Russia outlying economic, militiristic, diplomatic, and geopolitical cooperation between the two states.  

North America and Africa

•   Moroccan-American Treaty of Friendship – oldest continued military alliance with the United States.

North America and Asia

•   The U.S.–Afghanistan Strategic Partnership Agreement– an agreement between Afghanistan and the United States of America
•   The US-Israel Strategic Partnership Declares Israel a major strategic partner of the United States and allows a greater mutual cooperation in defense and other categories
•   Japan and the United States entered into a security alliance following the allied occupation after WWII.
•   Pakistan and the United States entered into a Mutual Defense Assistant Agreement following Liaquat Ali Khan’s state visit to the United States to counter Sino-Soviet ambitions in South Asia and Middle East.
•   The Mutual Defense Treaty is a joint US-Philippine Defence Treaty.
•   South Korea and the United States entered into a defense treaty following the Korean War.
•   The Taiwan Relations Act requires the United States to provide Taiwan with military equipment and optionally intervene militarily in the event of a Chinese invasion.

North America and Europe

•  NATO, Enlarged from 1999 to include eastern European states. North Atlantic Treaty only covers European, North American, and French Algerian (now independent and therefore not in force) territory.                            

North America and Oceania

•    ANZUS is a joint military alliance between the United States, Australia and New Zealand.

Tri-continental

• ABCA Armies, Air and Space Interoperability Council and AUSCANNZUKUS is collectively known as the Five Eyes –     
• Five Power Defence Arrangements     
• CANZUK is a proposed alliance between the major nations of the Commonwealth Realm.    

Global

• Multinational Force and Observers
•  United Nations
  • Department of Peacekeeping Operations
  • United Nations Security Council
• Major non-NATO Ally, allies of the United States, but not a member of NATO.                  
• Combined Maritime Forces (CMF) is a series of three 33 nation naval task forces, each with a specific role including; anti-piracy, anti-terrorism, and maritime security.^[2]                                 
• International Association of Gendarmeries and Police Forces with Military Status                
• International Maritime Security Construct, an alliance led by the United States dedicated to security in the Persian Gulf amid American tensions with Iran.