To which alliance did A.B. Vajpayee belong when he completed his tenure as the Prime Minister of India from October 1999 to May 2004?

National Democratic Alliance

A member of the Bharatiya Janata Party (BJP), Vajpayee was the tenth Prime Minister. He headed the BJP-led National Democratic Alliance in the Indian Parliament, and became the first Prime Minister unaffiliated with the Indian National Congress to complete a full five-year term in office.