Guru Nanak founded Sikhism and his followers were called Sikhs. The power of Sikhs increased in the northwestern part of India. The Sikhs became rulers of large part of the northwestern India. This is called the Sikh Kingdom or Empire. Ranjit Singh was the most famous ruler of the Sikh Empire. He expanded the borders of the Sikh Empire and at the time of his death, it covered areas of Punjab, and present day Kashmir and parts of Pakistan. The Sikhs and forces of the British Raj fought many wars. While Maharaja Ranjit Singh was alive, Britishers were not able to cross the Sutlej river. After his death, they took over the entire Punjab after battles with disorganised Sikh troops.