The First Anglo Sikh War was fought between the Sikh Empire and the East India Company between 1845 and 1846.
It resulted in partial subjugation of the Sikh kingdom.
The Sikh Army at that time was led by General Raja Lal Singh who, with Tej Singh, betrayed the Sikhs during the course of the war.
The Sikhs refused to allow the passage of British troops through their territory during the First Anglo-Afghan War (1838–42).
Having determined to invade British India under the pretext of forestalling a British attack, the Sikhs crossed the Sutlej River in December 1845.
They were defeated in the four battles of Mudki, Firozpur, Aliwal, and Sobraon.
The British annexed Sikh lands east of the Sutlej and between it and the Beas River; Kashmir and Jammu were detached, and the Sikh army was limited to 20,000 infantry and 12,000 cavalries.
The First Anglo Sikh War came to an end by the treaty of Lahore which was signed in 1846.
Treaty of Lahore:
The Treaty of Lahore was signed on 9 March 1846.
The Treaty was signed between the Governor-General Sir Henry Hardinge and two officers of the East India Company and the seven-year-old Maharaja Duleep Singh Bahadur and seven members of the Lahore Durbaracting on his behalf.
The terms of the Treaty were punitive.
The Sikh territory was reduced.
The Sikhs lost Jammu, Kashmir, Hazara, the territory to the south of the river Sutlej and the forts and territory in the JalandharDoabbetween the rivers Sutlej and Beas.