On November 8, 1855, in front of the Parroquia Church in the town square of the Nicaraguan city of Granada, a line of riflemen shot Gen. Ponciano Corral, the senior general of the Conservative government. Strangely, the members of the firing squad hailed from the United States. So did the man who had ordered the execution.  His name was William Walker. Though later generations would largely forget him, in the 1850s, he obsessed the American public. To many, he was a swashbuckling champion...