The First Sikh War (1845-1846) broke out when the Sikh army, under some provocation, crossed the Satluj. The Sikhs were defeated. They had to cede all their territories south of the Satluj, as well as the Jalandhar Doab (the land between the rivers Satluj and Beas).
Besides, they had to pay a huge war indemnity and cede Kashmir, which the British sold to Raja Gulab Singh of Jammu. The Sikhs revolted against these terms, but were suppressed.
After this the British placed the Sikh ruler under the Company’s protection, and posted a resident and a British force at Lahore.
Another Sikh revolt resulted in the Second Sikh War (1848-1849). The Sikhs were defeated, and Lord Dalhousie annexed Punjab in 1849.