Thanks for this additional data. Author David M. Sullivan has now confirmed that Isard of the CSS SUMTER, and Allen Cadwallader Izard, earlier in the U.S. Navy, and later in the 11th South Carolina Infantry, were indeed one and the same person. So he obviously tried to get back into the Confederate Navy, after resigning from the 11th SC in 1864, but there is no record that he ever did.