The Subsidiary Alliance was a strategic military-political system introduced by Lord Wellesley (1798–1805) to expand British influence in India.

Option A applies: A key feature was that the allied Indian state had to maintain a permanent British force within its territory and pay a subsidy for its maintenance, allowing the British to maintain a large standing army at the expense of the Indian ruler. Option C applies: The system was designed to counter the 'Napoleonic danger' by requiring Indian rulers to expel all non-British Europeans (especially the French) from their service and territory. Option D applies: By controlling the external relations and defense of the states, and placing a British Resident in the court, the Company effectively established British paramountcy (supreme authority) over the Indian states. Option B does not apply: Securing a 'fixed income' for the Company was the primary objective of land revenue systems, such as the Permanent Settlement introduced by Lord Cornwallis in 1793, rather than the Subsidiary Alliance which focused on military and diplomatic control.