Answer :
The foreign power here refers to France, which invated Mexico in 1861, and it established Mexico's only coronated head: Emperor Maximilian (brother of Austria's Franz Joseph).
The U.S. could not intervene at the time as it was engaged in its own Civil War (1861-1865).
The U.S. could not intervene at the time as it was engaged in its own Civil War (1861-1865).
