Sikhs fought Muslim invaders for 500 years?

"Along with Tej Singh, Lal Singh betrayed the Sikhs during the course of the war.
Lal Singh was regularly supplying information and even receiving instructions from British officers, communicating through Captain Peter Nicholson"

Jawahar Singh Aulakh (1814-1845)was Wazir of the Sikh Empire from 14 May 1845 until his assassination by the Sikh Khalsa Army on 21 September of the same year, under his nephew Maharaja Duleep Singh. He was the elder brother of Jind Kaur, Duleep's mother

Pashaura_Singh 1821 –1845
He is said to be the son of a slave girl in the household of Rani Daya Kaur. Procured by Daya Kaur and presented to, and accepted by Maharaja Ranjit Singh as his son.
After the assassination of Maharaja Sher Singh he made a bid for the throne of the Sikh Empire.

Maharaja Sher Singh (1807 –1843) was a son of Maharaja Ranjit Singh. In 1841, he became Maharaja of the Sikh Empire and the Punjab.
Sher Singh was killed as he reached for a new shotgun held by Ajit Singh Sandhawalia, who pulled the trigger. Sher Singh only had time to utter, "what treachery." The Sandhawalias also murdered Dhian Singh. The Sandhawalias were thought to have also had designs on the empire

Maharaja Jassa Singh Ramgarhia' (1723–1803) was a prominent Sikh leader during the period of the Sikh Confederacy Jassa Singh rose to command the Sikh misl that became later known as Ramgarhia and built a fort called Ram Rauni and Ramgarhia Bunga (watchtower) at Amritsar. He joined forces with Adina Beg, who appointed him a risaldar (commander), but switched sides