58-year-old Sitharaman, a Rajya Sabha member, is the second woman to take charge of the crucial ministry as Indira Gandhi, as the Prime Minister, had also held the portfolio in the seventies.
Her elevation is seen as reward for her good work as the Commerce Minister. Finance Minister Arun Jaitley was handling the Defence Ministry after Manohar Parrikar quit to become the Goa's chief minister in March.
"Somebody who has come from a small town, grown into the party with all the support of the leadership, and if given such responsibility, it just makes you feel sometimes that cosmic grace is there. Otherwise, it is impossible," she told reporters.
Sitharaman said she was just overwhelmed and humbled.
More From This Section
"I am sure, now that I have an extremely competent successor in Nirmala Sitharaman, she will carry the road forward," Jaitley said congratulating Sitharaman.
As the Defence Minister, Sitharaman will face several challenges, including strengthening of the combat capabilities of the Army, Navy and the Air Force due to changing regional security matrix and geo-political dynamics.
Defence experts feel the frequency of incidents of incursions by the Chinese Army may go up in the coming months and years after the Dokalam face-off, and Sitharaman may face a challenge in handling such complex issues.
The government has been focusing on domestic defence production and Sitharaman will have to carry forward a number of big-ticket reform initiatives, including implementing the ambitious "strategic partnership" model with several countries like the United States and Russia.
On August 30, the government had announced major reforms in the Indian Army to enhance its combat capability which will include redeployment of nearly 57,000 officers and other ranks. She will have to play a key role in implementing this initiative.
Sitharaman also faces the challenge of modernising the defence research organisations and various other defence public sector undertakings.
Parrikar's tenure as the Defence Minister saw the clearance of a raft of arms deals, besides simplification of the acquisition process. He had also pushed for a number of stalled acquisition projects.
Sitharaman is from Madurai in Tamil Nadu who had obtained a BA degree from Seethalakshmi Ramaswamy College in Tiruchirappalli and an MA degree in economics from the Jawaharlal Nehru University.