India had conducted five underground nuclear tests on May 11 and 13, 1998 in Pokhran in the Rajasthan desert and declared it crossed the nuclear threshhold.
Pakistan carried out nuclear tests a fortnight later.
The US and several other countries imposed harsh sanctions against India, denying it critical nuclear and space technology. Pakistan was also placed under sanctions.
India had faced international sanctions also after its first nuclear test in 1974.
One of the fallouts of the sanctions was that the country's atomic reactors operated way below their capacity due to lack of fuel. The worst hit were the two boiling water reactors at Tarapur, that required enriched uranium as fuel.
On the National Technology Day, marking the anniversary of the 1998 tests, President Ram Nath Kovind yesterday said the tests demonstrated the country's scientific capacity and political will and had a far-reaching impact on how the world came to see India.
After getting the NSG waiver, the US signed the historical nuclear cooperation agreement with India a decade later. India also reached civil nuclear cooperation accords with several other countries after that.
The deal with the US not only paved the way for India to gain access to critical space and nuclear technologies, it made import of supercomputers and high-technology equipment easier.
Since then, India has become a member of the Missile Technology Control Regime and the Wassenaar Arrangement. While India joined the MTCR in 2016, it entered the Wassenaar Arrangement on Export Controls for Conventional Arms and Dual-Use Goods and Technologies last year.
The NSG waiver was granted to India on September 6 that year allowing it to access civilian nuclear technology and fuel from other countries.
Following the waiver, France was the first country to sign a civil nuclear cooperation agreement with India.
India now has nuclear cooperation agreement with the UK, Russia, Australia, Japan, Canada, Argentina, South Korea, Kazakhstan, Namibia, Bangladesh, Sri Lanka and Vietnam.
Defence Minister Nirmala Sitharaman recalled the statement made by Atal Bihari Vajpayee, who as the prime minister, had announced the May 11, 1998 nuclear tests.
"'Today at 15:14, India conducted three underground nuclear tests in Pokhran range. The tests conducted today were with a fission device, a low yield device and a thermonuclear device.' --Former PM Shri Atal Bihari Vajpayee in a statement on #Pokhran2 (11/05/1998) @PIBIndia," she tweeted.
On May 13, 1998, India had detonated two sub-kiloton nuclear devices.
India has achieved nuclear triad capability having a structure to launch nuclear weapons from land, air and sea-based platform.
India acquired the capability with the launch of first indigenously built nuclear submarine INS Arihant in 2016.
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