Final answer:
The British excelled in diplomacy and military strategy during the post-War of 1812 era, leading to long-term peace and sovereignty, symbolized by agreements like Rush-Bagot and the Congress of 1818, and their dominance in India through the East India Company.
Step-by-step explanation:
The British were masters at treaty negotiation and building relationships with other governments, particularly after the War of 1812, where no decisive differences were settled. Seeking to maintain their global preeminence, the British utilized naval power and diplomacy to establish long-term peace, as seen with the Rush-Bagot Agreement that demilitarized the Great Lakes and the Congress of 1818, which set boundaries and fishing rights. Moreover, in India, the British East India Company's military prowess, combined with diplomatic negotiations, led to British dominance. This colonial reach and subsequent treaties via diplomatic channels ensured sovereignty and economic stability for the empire, demonstrating their acumen in foreign policy and military strategy.