India Detonated One Plutonium Device at Pokhran on 18 May 1974 and Five on 11 and 13 May 1998, and the Official Yield Claims for Both Are Still Disputed

At 8:05 a.m. on 18 May 1974, a member of the Bhabha Atomic Research Centre’s detonation team, P. R. Dastidar, pressed the button that fired a plutonium implosion device about 100 metres under the Rajasthan desert near Pokhran. The Department of Atomic Energy (DAE) estimated its yield at about 12 kilotons, and the government called the event a “peaceful nuclear explosion.” On 11 May 1998, 24 years later, Prime Minister Atal Bihari Vajpayee announced three underground tests at the same range, and two more on 13 May completed what the government called the planned series.

A kiloton is the blast energy of 1,000 tonnes of TNT. The official kiloton figures for both Pokhran dates are disputed, and this piece gives each disputed number to the person or body that stated it. The programme behind both dates was started under Homi Bhabha, whose career is covered in Homi Bhabha and the atomic programme.

What India told the world on the morning of 18 May 1974

Around 10 a.m., Foreign Secretary Kewal Singh telephoned the US embassy in New Delhi. Jayita Sarkar’s account, drawn from US diplomatic records, has him saying that the Atomic Energy Commission had carried out a “peaceful nuclear explosion” to keep India abreast of the technology for uses such as mining and earth moving. The chargé d’affaires, David Schneider, answered that Washington would receive the news with “considerable shock.”

The shaft had been dug by the Army’s 61 Engineer Regiment, which Sarkar says was first told by BARC director Raja Ramanna that the job was a “seismic experiment.” Villagers nearby were told that the Oil and Natural Gas Commission was prospecting for oil. A dry shaft collapsed in November 1973, killing one person, and in January 1974 another filled with water after the engineers struck an aquifer, so a new one had to be dug.

The fissile material was plutonium from the CIRUS research reactor, which Canada helped supply and for which the United States provided heavy water in 1956, according to Sarkar and the National Security Archive. Carey Sublette’s Nuclear Weapon Archive lists Ramanna as team lead, P. K. Iyengar as second in command, B. D. Nag Chaudhuri of the Defence Research and Development Organisation (DRDO) as coordinator, and R. Chidambaram as lead for the nuclear design, with no more than 75 scientists and engineers involved between 1967 and 1974.

The name “Smiling Buddha” comes from the date, which was Buddha Purnima. Sarkar writes that Ramanna reportedly phoned Prime Minister Indira Gandhi from an unsecured line with the words “The Buddha is smiling.” Sublette notes that the test had no formal code name before the shot and that the origin of the nickname is disputed. On 28 May 1974 Gandhi called India “a nuclear country, not a nuclear weapons country.” Ramanna said in 1997, as Sublette reports, that the test was “not all that peaceful.”

Historians also disagree on why the test happened when it did. Sarkar writes that US State Department officials and Ambassador Daniel Moynihan read it as an attempt to distract from domestic turmoil, including the railway strike of May 1974. Sarkar’s own reading is that Gandhi is believed to have given the formal approval in the fall of 1972, when she was politically strong after the 1971 war, and she adds that no paper trail of that decision has surfaced. She also records that Vikram Sarabhai told a Vienna conference in September 1971 that the DAE was working on the engineering of such explosive devices.

A yield of 12 kilotons, 8 to 10, or 4 to 6

The DAE’s figure was “about 12 kilotons.” At a technical meeting on peaceful nuclear explosions at the International Atomic Energy Agency (IAEA) in Vienna in January 1975, Ramanna and Chidambaram presented a BARC study that gave 12 kilotons, a seismic reading of 5.0 and a crater 47 metres in radius and 10 metres deep. The study said no radioactivity had been released, a claim Sarkar notes could not be independently checked.

Sarkar writes that the true yield “would become contentious” and has been put between 8 and 12 kilotons. Sublette’s table of estimates lists Iyengar at 8 to 10 kilotons, the US seismologist Terry Wallace at 4 to 6 kilotons in 1998, and Indian press reports at anywhere from 2 to 20. Sublette says that both Homi Sethna, the Atomic Energy Commission’s chairman in 1974, and Iyengar have conceded that 12 kilotons overstated it.

The suppliers’ club and the years of restraint

The National Security Archive’s documents show Henry Kissinger authorising a secret process in 1974 to set common export rules for sensitive nuclear technology. A first suppliers’ meeting took place in London in April 1975. The founding seven were Canada, France, Japan, West Germany, the United Kingdom, the United States and the Soviet Union, and the guidelines became public in February 1978 when the IAEA published them. That body became the Nuclear Suppliers Group.

Canada suspended its nuclear cooperation with India after the test, according to Sarkar, and in May 1976 it ended talks that had nearly produced a new agreement. The US Congress questioned the heavy water supplied to India. In 1977 the Janata government under Morarji Desai said publicly that India would conduct no further nuclear explosions, and Indian diplomats concluded that an invitation to the suppliers’ group would amount to the Non-Proliferation Treaty by the back door. In 1978 President Jimmy Carter signed a US law limiting nuclear aid to countries that accepted full-scope IAEA safeguards, meaning inspection of all their nuclear material and facilities.

Three attempts between 1995 and 1998

The National Security Archive, in a posting edited by William Burr, says US intelligence began picking up signs of test preparations at Pokhran in November 1995. The posting says analysts found the satellite photographs “as clear as mud.” Ambassador Frank Wisner showed Prime Minister P. V. Narasimha Rao’s principal secretary, A. N. Varma, a photograph in December 1995, and President Bill Clinton spoke to Rao by telephone in mid-December. The archive concludes that Rao authorised preparations but did not take the final step, partly from his own ambivalence about nuclear weapons.

In August 1996, when he led the opposition, Vajpayee told Wisner, “What if we start underground tests?” The archive adds that a test was suspended when Vajpayee left office in 1996 after less than two weeks as prime minister. A. P. J. Abdul Kalam said in 2011 that Rao had told him in May 1996 to proceed with preparations. Accounts differ on how far that went: Sublette writes that devices reached the test shafts before Vajpayee called the test off, while the National Security Archive says only that it was suspended.

Vajpayee was sworn in again on 19 March 1998. Sublette’s reconstruction, which does not cite sources, has him telling Kalam and Chidambaram on 20 March to be ready, and fixing 11 May after Kalam said a test needed about 30 days. Shakti Sinha, who was Vajpayee’s private secretary, wrote in 2018 that the prime minister’s residence had direct telecom links to Pokhran, that Vajpayee read a short statement in Hindi and English at a press briefing, and “There were a lot of tears in that room that day.”

What Vajpayee announced on 11 May and told Parliament on 27 May

The 11 May statement, as transcribed in news reports archived by the Berkeley Seismological Laboratory, said: “Today at 1545 hrs, India conducted three underground nuclear tests in the Pokhran range.” It listed a fission device, a low yield device and a thermonuclear device, and said the explosions were contained, like the 1974 experiment. It did not call them peaceful.

A joint statement from the DAE and DRDO on 17 May gave the figures: a fission device of about 12 kilotons, a thermonuclear device of about 43 kilotons and a sub-kiloton device on 11 May, then two sub-kiloton devices of 0.2 to 0.6 kilotons on 13 May. At the press conference that day Chidambaram said the nearest village, Khetolai, is a little over 5 km away and that this distance set the total yield.

On 27 May Vajpayee told Parliament: “India is now a nuclear weapon state. This is a reality that cannot be denied.” He added, “We do not intend to use these weapons for aggression or for mounting threats against any country.” The moratorium announcement is in the same statement: “India will now observe a voluntary moratorium and refrain from conducting underground nuclear test explosions,” and he said the government was willing to make that binding in law.

The words “no first use” are not in that statement. The paper tabled the same day, Evolution of India’s Nuclear Policy, recalls India’s 1994 proposal that India and Pakistan jointly pledge not to be first to use nuclear weapons against each other, and says the government reiterated its readiness to discuss a no-first-use agreement with that country and others. A unilateral posture appears in the National Security Advisory Board’s draft doctrine of 17 August 1999: “India will not be the first to initiate a nuclear strike, but will respond with punitive retaliation should deterrence fail.”

Claimed yields against measured ones

The 11 May claim of about 12 kilotons for the fission device and about 43 for the thermonuclear one implies roughly 55 kilotons, before counting the sub-kiloton device. Outside seismologists measured far less. BARC’s own November 1998 newsletter, replying to critics, lists Terry Wallace at 10 to 15 kilotons for the three 11 May shots, from a US Geological Survey body-wave magnitude (a seismic scale) of 5.2, and Brian Barker and colleagues at 9 to 16 kilotons from a magnitude of 5.0 reported by the International Data Centre that processes monitoring data for the test-ban treaty. Barker’s group put the 13 May shots at 30 to 300 tonnes.

BARC’s authors, S. K. Sikka, Falguni Roy, G. J. Nair, V. G. Kolvankar and Anil Kakodkar, argued for 58 kilotons, give or take 5, from a corrected magnitude of 5.39 and a comparison with the 1974 test. The Hindu reported in 2009 that BARC scientists calculated 50 kilotons, give or take 10, for the thermonuclear test, and that samples taken after the shot showed sodium-22 and manganese-54, by-products of fusion rather than of fission alone. Chidambaram has said that Western seismologists underestimated because they ignored the local geology, and that the 13 May shots went unseen by international monitors because of the higher detection threshold there.

Others sit between the camps. Sublette’s own analysis puts the thermonuclear shot at about 31 kilotons. In 2000 Iyengar said the second stage of that device had worked only partly, and BARC denied it, according to Sublette. In August 2009 K. Santhanam, who represented DRDO’s team at Pokhran-II, said the thermonuclear yield was “much lower than what was claimed.” Chidambaram, then the government’s Principal Scientific Adviser, answered in The Hindu’s report that such a charge needs scientific evidence.

The 1998 sanctions and how they were lifted

President Clinton signed Presidential Determination 98-22 on 13 May 1998, finding that India had “detonated a nuclear explosive device on May 11, 1998.” The Congressional Research Service lists the penalties under the Arms Export Control Act: an end to most foreign aid, to arms sales and to military financing, a ban on US government credit, US opposition to loans from international financial institutions, a ban on US bank loans to the government, and export controls. The Export-Import Bank also stopped new financing for India. The Group of Eight countries agreed to postpone non-basic-needs loans from those institutions.

Asked about sanctions on 17 May, Kalam said: “Technologically, we have faced sanctions for a long time.” The Arms Control Association records that Deputy Secretary of State Strobe Talbott set five goals, among them signing the Comprehensive Test Ban Treaty and halting fissile material production, and that India and Pakistan said in September 1998 they would sign the test-ban treaty by September 1999. Neither accepted the fissile material or missile limits.

Relief came in steps. Congress passed the India-Pakistan Relief Act on 21 October 1998, and Clinton used it from 1 December 1998 to restore Export-Import Bank and Overseas Private Investment Corporation support and lift limits on US banks, though arms sales stayed barred. A law of 25 October 1999 let the President waive the sanctions with no time limit, and on 22 September 2001 President George W. Bush waived the defence-sales, technology and military-financing sanctions and any remaining ones for both India and Pakistan, the Congressional Research Service reports.

The doctrine announced on 4 January 2003

On 4 January 2003 the Cabinet Committee on Security released a summary of India’s nuclear doctrine. It lists “a credible minimum deterrent,” a posture of no first use under which nuclear weapons are used only in retaliation for a nuclear attack on Indian territory or on Indian forces anywhere, and retaliation that “will be massive and designed to inflict unacceptable damage.” Only the civilian political leadership, acting through the Nuclear Command Authority, can authorise it. How that doctrine sits behind India’s response to terror attacks today is covered in How India answers an attack.

The same statement says India will not use nuclear weapons against states without them, but keeps the option of nuclear retaliation after a major biological or chemical attack on India or its forces anywhere. It commits India to export controls, to the fissile material treaty negotiations and to “continued observance of the moratorium on nuclear tests.” It also approved the appointment of a Commander-in-Chief of the Strategic Forces Command and alternate chains of command for retaliatory strikes.