Profile: Lal Krishna Advani
Known for his formidable organising skills, LK Advani is credited with scripting the rise of India's main opposition Bharatiya Janata Party (BJP) as a major political force.
Mr Advani, 85, helped take the party from two parliamentary seats in 1984 to government within 15 years.
The veteran leader's announcement on 10 June that he was resigning from all party positions therefore came as a surprise.
In recent years, say analysts, Mr Advani has been upstaged by the younger guard of the party, led by the charismatic Gujarat chief minister, Narendra Modi, who will lead the party's campaign in the 2014 general elections.
Media reports say Mr Advani was upset over Mr Modi's elevation as head of the BJP's election committee, the day before he sent his resignation letter.
Many have seen Mr Advani as a divisive figure who exploited Hindu-Muslim tensions, remembering him for the campaign he led to have a Hindu temple built on the site of a destroyed mosque in the flashpoint northern city of Ayodhya.
He attempted a makeover during the last decade, reaching out to young voters who now comprise a substantial chunk of the electorate.
He launched his own website and blog, and during a campaign stop during the 2009 general election, he appeared at a gym in India and was seen checking out the equipment.Hawk
Mr Advani served as deputy prime minister in the government of Atal Behari Vajpayee until its general election defeat in May 2004, before stepping up to lead his party.
Yet it is the campaign over Ayodhya that has marked Mr Advani's career.
In 1990, Mr Advani travelled across India, whipping up support for a campaign to build a temple on the site of the 16th Century Babri mosque in Ayodhya.
That led to violent scenes there with the destruction of the mosque by Hindu hardliners, followed by some of India's worst religious violence since partition in 1947.
Mr Advani has fought ever since to clear his name after allegations that he incited the mobs.
Whatever the outcome, his critics will always accuse him of having encouraged communal polarisation, detrimental to the secular credentials of India.
His supporters, however, say the campaign galvanised an entire generation and drew millions of supporters to the party which went on to help reshape India's economy and its image in the post-Cold War world.Disciplinarian
Mr Advani was born in Karachi in what is now Pakistan and his family moved to India just before partition.
He was a member of the Rashtriya Swayamsevak Sangh (RSS), the Hindu nationalist organisation from which the BJP draws its ideological roots.
Mr Advani had a reputation as an efficient and honest - if at times ruthless - administrator with considerable analytical skills.
He is well known as a cricket and Bollywood buff - favourites are batsman Sachin Tendulkar and actor Amitabh Bachchan - and an enthusiast for the writings of Alvin Toffler about the need to adapt to a changing world.
He once told the BBC that he keeps fit by eating frugally.
Mr Advani also has a reputation for being a strict disciplinarian and a family man.Troublesome allies
It was as part of his attempt to reposition himself politically and cast off his hawk's clothing that he made a landmark six-day trip to Pakistan in June 2005.
By adopting a more moderate tone, Mr Advani would make himself more palatable to a broader electoral base, the theory went.
But his praise for Pakistan's founder Mohammed Ali Jinnah, and his description of him as secular, aroused anger and controversy in India.
He offered to step down as party president after he found himself isolated within the BJP and criticised by Hindu nationalist pressure groups which regard the founder of Pakistan as the architect of the partition of India along communal lines.
Mr Advani also had problems with his coalition.
A loyal regional ally in Orissa, the Biju Janata Dal (BJD), parted ways with the BJP - and some of the blame was laid at Mr Advani's door.
Running a national party and a government in India these days is mostly about wooing allies and managing coalitions - a job in which Mr Advani's predecessor, Mr Vajpayee, excelled.
Mr Advani has had no such luck as the BJP-led National Democratic Front (NDA) alliance lost the 2009 elections.
Since then, the younger guard of the party, led by Mr Modi, have exerted their influence in the BJP.