Topic

The Gorkha Invasion — Nature and Consequences

A named syllabus topic, so it is worth a full structured answer: causes, course, nature, consequences.

Causes

Gorkha ambition after the unification of Nepal by Prithvi Narayan Shah (1768) — a kingdom 'from Nepal to Kashmir'.
The fragmentation of the hill states into some thirty mutually hostile units.
Sansar Chand's own overreach: the chiefs he had reduced to tribute, led by Kahlur, invited the Gorkhas in against him.

1803 — Amar Singh Thapa crosses the Yamuna and takes Sirmaur.
1804–05 — the Shimla hill states submit; the Gorkhas reach the Sutlej.
1806 — Battle of Mahal Morian: Sansar Chand defeated; Gorkhas overrun the Kangra valley and besiege the fort for four years.
1809 — Ranjit Singh, invited by Sansar Chand, drives the Gorkhas back across the Sutlej and keeps Kangra fort.
1814–16 — the Anglo-Gorkha War: Gillespie killed at Kalanga (31 Oct 1814); Jaithak holds out; Ochterlony takes Ramgarh and then Malaun (15 May 1815).

Military occupation, not administration — the object was revenue and manpower, not government.
Heavy and arbitrary revenue demand; begar (unpaid forced labour) on a large scale.
Slave trade and the sale of people for arrears — the most frequently cited grievance.
Destruction of temples and forts; depopulation of tracts in Sirmaur and the Shimla hills.
But also: a single authority imposed across thirty quarrelling states for the first time, which made the later British settlement possible.

End of hill-state independence — the rajas were restored in 1815, but as protected states holding British sanads.
British territory in the hills — Subathu, Kotgarh, Kotkhai, and the land that became Shimla were retained directly.
A Superintendent of Hill States was appointed at Subathu; the agency system followed.
Gorkha recruitment into the British army; the Nasiri battalion (later 1st Gorkha Rifles) raised from the surrendered troops.
Permanent fixing of the boundary at the Kali river by the Treaty of Segauli.