Twenty years ago, on May 11, 1998, the then Indian prime minister Atal Bihari Vajpayee declared a nuclear power with the tests at Pokhran.

Much has been written in the Indian media on how Indian intelligence, aware of US spy satellites and the interest of the CIA in trying to detect the country's nuclear test preparations, hoodwinked the Americans and used codes which were so detailed and camouflaged that even the actual writers of the cryptogram were at times stuck deciphering these.

Americans also bemoaned how their intelligence agencies blundered and termed it “the intelligence failure of the decade”.

Pokhran II: 10 Key facts

The preparations began almost ten days before the tests with the weapons being transported from BARC in Mumbai to Pokhran on May 1. So as to not attract any attention, minimal security was used and only four trucks transported the devices instead of an elaborate convoy.

The preparation went on under the noses of the Americans (satellites). Digging of the shafts took place only at night and heavy equipment was placed back in the same place every morning to avoid detection. The earth dug out was shaped to make it appear like a sand dune.

With Pokhran range full of Army soldiers, the scientists too had to wear camouflage combat dress. This was done to help them move around without issues and not stand out and attract attention. Dr APJ Abdul Kalam, for example, went by the code name Major General Prithviraj.

Three devices were tested on 11 May and two more on 13 May. The devices were identified as Shakit-I to Shakti-V, and the shafts that were used for tests were named White House (Whiskey), Taj Mahal (Tango) and Kumnbhakaran (Kilo).

The direction of the wind was a key factor on the day the test was conducted. The wind was blowing towards inhabited areas in the morning, and this led to the risk of radiation spreading in case of a leak after the explosions. By noon the wind and died down and the tests took place.

Two keys were used to detonate the devices simultaneously. One key each was handed over to the representatives of BARC and DRDO who turned them together.

Nuclear devices tested on 11 May were of three different designs – a 45 kT thermonuclear warhead that used nuclear fusion, a pure fission device of 12 kT yield designed to be dropped from an aircraft and an experimental fission device of 0.3 kT yield.

Two more devices were exploded on May 13. This was done, not to boast or outdo any nation, but to generate additional data for use in computer simulations. The shaft used was codenamed Navtala, because of the presence of 9 dry wells in the area.

A third device and shaft was also prepared but never fired.