The Chagai Hills are granite mountains, which, at their highest point, rise to a height of 9,367 ft (3,009m) above sea level. They stretch over an area that is approximately 175 km in length and 95 km in width.
The Chagai Hills lie in an arid zone, which is outside the main monsoon belt. The Chagai Hills receive scanty and irregular rainfall (an average of 4 inches (102 mm) annually). The temperature is extreme: very hot in summer and very cold in winter. The average minimum temperature is 2.4 °C (36.3 °F) in January and the average maximum temperature is 42.5 °C (108.5 °F) in July.
Chagai Hills are often confused as being the location of Pakistan's nuclear tests of 28 May 1998, which were not carried out in the Chagai Hills but in the Ras Koh Hills, which is an entirely different range of hills to the south of Chagai Hills and separated from the Chagai Hills by a large valley. The confusion may arise from the fact that both the Chagai Hills and the Ras Koh Hills are situated in the Chagai District with the same name.
Plans to conduct tests were begun by Münir Ahmad Khan, Chairman of the Pakistan Atomic Energy Commission (PAEC) in 1975. The PAEC's Directorate for Geological and Seismic Development (GSD) completed the survey finding a suitable locations for the weapon-testings site. In 1976, after the formal reported was submitted, Munir Ahmad Khan summoned dr. Ishfaq Ahmad, Director-General of Nuclear Physics Group (NPG) and Dr. Ahsan Mubarak, Director-General Geological and Seismic Development (GSD) and, tasked them for the selection of the nuclear test sites. In 1976, Bhutto directed an electronic telegram, through Army Generals Headquarter (GHQ), to Brigadier-General Muhammad Sarfraz, Chief of Staff of the 17th Mountain Brigade of the V Corps. The message was to make an availability of a Mil Mi-8, an army helicopter, to a forthcoming team of civilian scientists from PAEC for operational reconnaissance mission of some areas in Balochistan Province. At 4:00 a.m., the small teams of physicists and seismologist landed at the Samungli Air Force Base and at 06:00 hours, the Mil Mi-8 took off the teams under Ishfaq Ahmad and Dr. Ahsan Mubarak. Over a span of three days, the PAEC scientists reconnoitered, several times, the area between Turbat, Awaran and Khüzdar to the south, Naukundi to the east and Kharan to the west. One of the objective was to find a suitable place for an underground tests, preferably a mountain. After a hectic and careful survey, the mountain was discovered at Ras Koh Hills, an area completely independent from Chagai Hills. It is noted that Ras Koh Hills are not located in Chagai Hills and independent from the region. But, because Ras Koh Hills are located in Chagai District, it is often confused with Chagai Hills.
With incoming Martial Law Administrator General Rahimuddin Khan, the PAEC began to construct its iron-steel underground tunnels in 1977 and PAEC completed its construction in 1979. The task was undertaken by the Corps of Engineers's Special Development Works (SDW) and Frontier Works Organisation (FWO), the special units of military scientists and engineers, headed by Lieutenant-General Zahid Ali Akbar Khan and Brigadier-General Muhammad Sarfaraz, directly reporting to the Pakistan Army's Generals Headquarters (GHQ). The primary task of the organization was to prepare underground test sites (both horizontal and vertical shafts) for 20-kilotonne nuclear devices, with all the allied infrastructure and facilities. The sites had to be designed in such a way that they could be utilized at short notice (in less than a week) and were to be completed by December 1979 at the latest.
Long before the tests be concluded, American authors William E. Burrows and Robert Windrem, published their book, Critical Mass, in 1994. Through this book, the Chagai Hills nexus with nuclear deterrent programme of Pakistan became the focus of international attention. However, despite of its notoriety, none of the nuclear tests were conducted in the Chagai Hills.
However, because the related mountains in which the tests were performed were in the Chagai District, global intelligence agencies thought that the Chagai Hills were the test site for the weapon-testings. These tests were followed by India, which surprisingly conducted the tested its own nuclear devices —codename Operation Shakti — on May 11 and May 13, the Pokhran-II, in the Pokhran Army Test Range (PATR) located in the Rajasthan State, an eastern border of Pakistan. After Prime minister Nawaz Sharif attended the National Security Council's session, Sharif ordered and gave authorization to the academic scientists at the Pakistan Atomic Energy Commission (PAEC) to conduct a nuclear test operation of its own. Following the orders, scientists from Kahuta Research Laboratories (KRL), Defence Science and Technology Organization (DESTO), Corps of Engineers and Military Engineering Service (MES) also joined PAEC in the efforts. Ordered by Prime minister Sharif, No. 11 Squadron Arrows was put on high-alert and the No. 6 Squadron Globe Trotters flew the nuclear devices, in sub-assembly form, to the Chagai District. Meanwhile, the Ahsan Naval Base and the Naval Observatory was also at red-alert level providing electronic intelligence services to the Pakistan Armed Forces.
On May 25, the preparations were completed by PAEC, and the iron-steel tunnels were closed with mixed sand-cement. On May 26, the iron-steel tunnels were electronically plugged, and on May 27, after the cement had completely dried out due to the excessive heat of the summer desert, the engineers certified that the concrete had hardened and the site was fit for the tests. This was communicated to the Prime Minister via the GHQ notifying him that the site was ready. The Naval Observatory set the time and date for operation for 3:00 p.m. on 28 May 1998.
On May 28, the PAEC conducted a nuclear tests of five nuclear devices, exploded simultaneously, at 15:00 hours. This operation was named Chagai-I. All of the nuclear devices used HEU, evidently made from KRL, and had Beryllium reflectors.
After the tests, the Pakistan Government did not issue any additional details about exact locations of where the tests were performed. The Chagai District is an extensive and dangerous areas and the sites are not under the safeguards or inspections of the International Atomic Energy Agency (IAEA).
- Burrows, William; Robert Winderm (1994). Critical Mass''. Washington D.C.: Simon and Schuster. p. 384. ISBN 978-0-671-71096-5.