Lal Bahadur Shastri was the 2nd Prime Minister of India. His premiership lasted less than 2 years, as Shastri died in the city of Tashkent in Soviet Union.
Succession of Nehru
On Nehru’s death, then Congress President K. Kamaraj started looking for the best person to succeed Nehru as Prime Minister. Morarji Desai was a probable candidate, however it seems that most MPs preferred Lal Bahadur Shastri instead. Shastri was also very close to Nehru in his last days, wchich was probably helpful.
Anti Hindi Agitation in Madras, 1965
There were intense anti-Hindi protests against the Central Government which was trying to make Hindi the official language for all government work in 1965. The protests eventually succeeded, with Shastri speaking on All-India Radio to assure that states would not be forced to use Hindi unless they want to. The Indian Civil Services exam would also continue to be conducted in English.
Shastri was in support of Hindi being the sole official language of India, but was forced to reconsider after the protests. 
War with Pakistan, 1965
Shastri was a major player in the Indo-Pakistan war of 1965 . When Pakistan sent over armed belligerents with the hope of sparking a revolt in Kashmir (see Operation Gibraltar ), Shastri retaliated by attacking West Punjab, aiming for Lahore.
Shastri was also different from Nehru in the war response, in the sense that he was decisive and swift to order the strike across the Punjab border . In comparison, Nehru had refused to call in the air force during the Indo China war 
Shastri went to Tashkent to sign a peace treaty with Ayub Khan, the Pakistani president. Soviet prime minister, Alexei Kosygin was the chieft mediater. The Tashkent agreement mandated withdrawal of forces to positions they held before August 5, 1965 and ordery transfer of prisoners of war.
Shashti died in his sleep of a heart attack, the night the agreement was signed.