Step 1: Recall the year directly:
1801 A.D. marks: Subsidiary Alliance imposed on Awadh.
Step 2: Provide brief context:
In 1801, the Nawab of Awadh was compelled to cede a large part of his territory (the Doab and Rohilkhand region) to the British East India Company under the Subsidiary Alliance system.
Final Answer:
\[ \boxed{\text{Subsidiary Alliance imposed on Awadh}} \]