During the Vajpayee administration between 1998 and 2004, he held multiple cabinet portfolios including Finance, External Affairs and Defence.

[13] In the aftermath of India's nuclear tests of 1998, he was deputed by Prime Minister Vajpayee to act as India's representative to hold repeated, long-term dialogue with the United States (represented by Strobe Talbott) on matters related to nuclear policy and strategy; the outcome of the sustained engagement was positive for both countries.

[27] After his education from the National Defence Academy, he was enrolled in the Indian Army in the year 1957 and was designated to the position of the Captain in the Central India Horse unit.

[33] Singh is widely regarded for his handling of relations with the United States which were strained after the 1998 Indian nuclear tests but which ameliorated soon after culminating in the 2000 visit of U.S. President Bill Clinton to India.

[35] Singh was denied a Member of Parliament ticket for Barmer by BJP for the 2014 Indian general election over Col. Sonaram Choudhary.

He tasted success in his political career in 1980 when he was first selected for the Rajya Sabha, the upper house of Indian parliament.

[16] He was denied a ticket by the party to contest the 2014 Lok Sabha Parliamentary Elections from the Barmer-Jaisalmer constituency in Rajasthan.

[45] Jaswant Singh held many ministries under the government of Atal Bihari Vajpayee, including several important such as Defence, External Affairs and Finance.

As the Minister of External Affairs he launched the first free-trade agreement (with Sri Lanka) in South Asia's history, initiated India's most daring diplomatic opening to Pakistan, revitalised relations with the US, and reoriented the Indian military, abandoning its Soviet-inspired doctrines and weaponry for close ties with the West.

[56] At that time after the successful test of the Second Nuclear Bomb it was considered a masterstroke by the government, it was said that Singh along with Atal Bihari Vajpayee and George Fernandes were the one who played the important role in the functioning.

[65] After that Singh made an interview with Atal Bihari Vajpayee in which to strengthening the position of Indian Government there was a release of a leaked conversation of Pervez Musharraf in which he admitted that he was involved in the attack on India in Kargil district in 1999 and that he also planned an attack to kill Nawaz Sharif and become the President of Pakistan.

[66] This was known to be a masterpiece and led to a very strong point resulting in the India's diplomatic relations and proving the burden of war on General Musharraf.

[68] The terrorists of Taliban hijacked the Indian Airlines Flight 814 on 24 December 1999 on the Tribhuvan International Airport of Kathmandu, Nepal.

[75] The incident is seen as a failure of the BJP government under Prime Minister Atal Bihari Vajpayee and IB chief Ajit Doval said that India would have had a stronger negotiating hand if the aircraft had not been allowed to leave Indian territory.

[76] Doval, the IB chief, who led the four-member negotiating team to Kandahar, described the whole incident as a "diplomatic failure" of the government in their inability to make the US and UAE use their influence to help secure a quick release of the passengers.

[87][88] Jaswant Singh was appointed as the Member of Parliament of Rajya Sabha for the fourth time in the year 1999 and after the formation of the Vajpayee Government he was appointed as the Leader of Rajya Sabha on 13 October 1999 and remained till the time of fall of the Vajpayee Government on 22 May 2004 and succeeded the position to then Prime Minister, Manmohan Singh.

[91] After the fall of National Democratic Alliance in the year 2004 and the weakening of senior-BJP leaders like Atal Bihari Vajpayee, Murli Manohar Joshi, Lal Krishna Advani and the politics of other big leaders like Bhairon Singh Shekhawat in central level, Singh as the leader of Opposition shifted his politics for the strengthening of the party in ground roots and in state levels in states of Western India such as Gujarat, Madhya Pradesh and specially Rajasthan.

Singh had filed his nomination papers on 20 July in the presence of National Democratic Alliance coalition leaders.

[94] Three sets of papers- one each by L. K. Advani, Sumitra Mahajan and Yashwant Sinha, supporting Singh's candidature were submitted to the returning officer Viswanathan.

[95] He meet All India Anna Dravida Munnetra Kazhagam leader Jayalalithaa and Naveen Patnaik of Biju Janata Dal on 6 August asking them to support his candidature.

[97] It is with profound grief that we inform you about the sad demise of Hon’ble Major Jaswant Singh (Retd), former Cabinet Minister of Government of India at 6:55 a.m. on September 27, 2020.

He was admitted on June 25, 2020, and being treated for Sepsis with Multiorgan Dysfunction Syndrome and effects of Severe Head Injury old (Optd) had a cardiac arrest this morning,” In June 2020, Singh was admitted to the Delhi's Army Hospital and was being treated for sepsis with multi-organ dysfunction syndrome and effects of a severe head injury he suffered as a result of a fall in 2014.

[107] His last rites were done by his son Manvendra Singh and was cremated in Jodhpur, Rajasthan with full Hindu rituals.

Prime Minister Narendra Modi reacted on his death stated that "Jaswant Singh Ji served our nation diligently, first as a soldier and later during his long association with politics.

During Atal Ji's Government, he handled crucial portfolios and left a strong mark in the worlds of Finance, Defence and External affairs.