"Old Hickory" was the nickname for the American president. The soldiers contributed to the unity of the troops from different states as part of the war effort.
It is the term given to one of the army units of the North Carolina soldiers that fought in the war. It is the nickname used for president Andrew Jackson.
The name depicts the strong determination and toughness like that of the hickory tree. The troops of the North Carolina soldiers united the soldiers from various states and led the war against Germany.
Therefore, option D. the troops united soldiers from different states.
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