19世纪40年代

The 1840s was a decade marked by major geopolitical shifts, including the Mexican-American War that expanded U.S. territory westward, Britain's colonization of New Zealand following the Treaty of Waitangi, and the First Opium War that opened Chinese ports to European imperial control. This period matters because these events reshaped national boundaries, colonial relationships, and global power dynamics that would influence international relations for decades to come.

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