Premise: During the reign of his son, under a regent, the borders were pushed further north and west, provoking reactions from the Tibetans and Chinese as well as the British East India Company, the power to the south.

Hypothesis: The borders were pushed further west and north under the reign of his song,  under a regent, and that provoked reactions from the Tibetans and Chinese as well as the British East India Company, the power to the south.
Relation: entailment