Explanation:

The roots of NAM went back to the friendship between three leaders — Yugoslavia’s Josip Broz Tito,  India’s Jawaharlal Nehru, and Egypt’s leader Gamal Abdel Nasser — who held a meeting in 1956.  Indonesia’s Sukarno and Ghana’s Kwame Nkrumah strongly supported them. These five leaders came  to be known as the five founders of NAM. The first non-aligned summit was held in Belgrade in 1961. 
This was the culmination of at least three factors:
(i) cooperation among these five countries,
(ii) growing Cold War tensions and its widening arenas, and
(iii) the dramatic entry of many newly decolonised African countries into the inter - national arena. By  1960, there were 16 new African members in the UN. The first summit was attended by 25 member  states. Over the years, the membership of NAM has expanded.