India's closest friend during the Cold War years was the Soviet Union.

The Cold War was a period of geopolitical tension and ideological conflict between the United States and the Soviet Union, which lasted from the end of World War II until the early 1990s. During this time, countries around the world aligned themselves with either the US-led Western bloc or the Soviet-led Eastern bloc, based on their political ideologies and strategic interests. India, under the leadership of Prime Minister Jawaharlal Nehru, adopted a policy of non-alignment and sought to maintain friendly relations with both superpowers. However, it was the Soviet Union that became India's closest friend and ally during this period.

Support for India's Independence Struggle:
- The Soviet Union had been supportive of India's independence struggle against British colonial rule. It recognized India as an independent nation even before its formal independence in 1947.
- The Soviet Union's support for India's independence movement created a sense of gratitude and goodwill among the Indian leadership towards the Soviet Union.

Political and Economic Cooperation:
- India and the Soviet Union shared a common political ideology of socialism, which further strengthened their ties. Both countries were committed to non-alignment, decolonization, and promoting self-determination for developing countries.
- The Soviet Union provided political and economic support to India. It assisted India in various development projects, such as the establishment of heavy industries, infrastructure development, and the Green Revolution in agriculture.
- The Soviet Union also supported India in international forums, such as the United Nations, by advocating for India's interests and supporting its positions on various global issues.

Military Cooperation and Defense:
- The Soviet Union became India's primary supplier of military equipment and technology. It provided India with advanced weaponry, including tanks, aircraft, missiles, and naval vessels.
- The Soviet Union also supported India during times of conflict, such as the India-China war in 1962 and the India-Pakistan wars in 1965 and 1971. It provided military aid and diplomatic support to India during these conflicts.

Cultural and People-to-People Exchanges:
- India and the Soviet Union promoted cultural exchanges and people-to-people contacts. There were educational and cultural exchange programs, which helped in strengthening the bonds between the two nations.
- The Soviet Union also hosted Indian students, scholars, and artists, who gained exposure to Soviet culture, education, and scientific advancements.

Conclusion:
- The Soviet Union emerged as India's closest friend during the Cold War years due to their shared political ideology, economic cooperation, military support, and cultural exchanges. The strong relationship between India and the Soviet Union was based on mutual trust, respect, and common interests. However, it is important to note that India maintained relations with other countries as well and pursued a policy of non-alignment, which allowed it to maintain independence and autonomy in its foreign policy decisions.