Complex sentence: Early in his governorship, Wellesley adopted a policy of non-intervention in the princely states, but he later adopted the policy of forming subsidiary alliances, which played a major role in British expansion in India.
Split into simpler sentences: Early in his governorship Wellesley adopted a policy of non-intervention in the princely states, but he later adopted the policy of forming subsidiary alliances. This policy was to play a major role in British expansion in India.