An example of a functioning military alliance is:

(1) NATO
(2) CENTO
(3) SEATO
(4) WARSAW PACT

1

An example of a functioning military alliance is (1) NATO (North Atlantic Treaty Organization). NATO is a prominent and long-standing military alliance formed to ensure the collective defence of its member countries. The North Atlantic Treaty Organisation (NATO) came into existence in April 1949. It was an association of twelve states which declared that an armed attack on any one of them in Europe or North America would be regarded as an attack on all of them. Each of these states would be obliged to help the other.

CENTO (Central Treaty Organization), also known as the Baghdad Pact, became inactive in 1979. It was a military alliance formed in 1955, which included the United Kingdom, Iran, Iraq, Pakistan, and Turkey. However, CENTO's effectiveness had diminished over the years, and it formally disbanded in 1979.
SEATO (Southeast Asia Treaty Organization) became inactive in 1977. SEATO was a collective defence organization formed in 1954 to counter the spread of communism in Southeast Asia. However, it lost its relevance over time, and the organization officially dissolved in 1977.
The Warsaw Pact, a military alliance among Eastern Bloc communist countries, formally became inactive on July 1, 1991. The dissolution of the Warsaw Pact occurred as a result of the political changes and the end of the Cold War in Europe, which led to the disintegration of the Eastern Bloc and the eventual collapse of the Soviet Union.