When the Union was fighting to preserve itself in the Civil War, the France of Napoleon III moved troops into Mexico, overthrew the regime of Benito Juarez, set up a monarchy and put Austrian Archduke Maximilian von Habsburg on the throne as Emperor of Mexico — one month before Gettysburg.
Preoccupied, the Union did nothing.
At war’s end, in 1865, however, at the urging of Gens. Ulysses S. Grant and William Sherman, the Union sent 40,000 troops to the Mexican border.
Secretary of State…