In 1809 the reigning Ameer of Afghanistan, Shah Soojah-ul-Moolk, was
dispossessed of his throne and an exile. Runjeet Singh, the Sikh ruler
of Punjaub, plundered and imprisoned him at Lahore, and obtained from
him the famous Koh-i-noor, the great diamond which is now among the
crown jewels of Great Britain. Eventually Soojah escaped from Lahore
and became a pensioner of the East India Company. For many years after
the fall of Shah Soojah, anarchy ruled in Afghanistan, until in 1826
Dost Mahomed established himself upon the throne at Cabul.
Meantime Shah Soojah never ceased to plot for his restoration, and in
1832 came to an agreement with Runjeet Singh, in pursuance of which the
latter undertook to assist him in an armed attempt to oust Dost Mahomed.
The Indian Government, while professing neutrality, indirectly assisted
Shah Soojah by paying his pension in advance.
In 1833 Shah Soojah's army was thoroughly beaten by Dost Mahomed before
Candahar, though he himself escaped. But Runjeet Singh was more
successful; he drove the Afghans back into the Khyber Pass and occupied
Peshawur, which province he held against all the attempts of the Afghan
Ameer to expel him.
In 1837 the Shah of Persia, under the instigation of and with assistance
from, Russia, and in spite of strong remonstrances by the British, made
war upon Afghanistan and marched upon Herat.