Sikhism achieved a series of military victories and created a Sikh Empire in 1799. The Sikh empire had its capital in Lahore, spread over almost comprising what is now northwestern Indian subcontinent. The Sikh Empire entered into a treaty with the colonial British powers, with each side recognizing Sutlej River as the line of control and agreeing not to invade the other side. Ranjit Singh's most lasting legacy was the restoration and expansion of the Harmandir Sahib, most revered Gurudwara of the Sikhs, with marble and gold, from which the popular name of the "Golden Temple" is derived. After the death
Nishan Sahib Sahib can be seen from far away, signifying the presence of Khalsa in the neighbourhood. It is taken down every Baisakhi (harvest festival, mid-April in the Gregorian calendar), and replaced with a fresh flag, and the flagpole refurbished. During the times of Guru Amar Das the Nishan Sahib was white, to represent peace and simplicity. During the time of Guru Hargobind, however the Nishan Sahib changed into a shade of yellow, known as Basanti. After the creation of Khalsa, Guru Gobind Singh introduced blue flag, which is still the colour of the Nihang flags. The first Sikh flags were plain,