"After he came back he married the widow xxx."

What is the name, age, etc. of Grandma. When, where were they married? & any other clues.

I suspect the missing John was conscripted and deserted when the occasion arrived. Here’s a possibility:
…………..

John Strong, Private , Company E, Armistead’s Regiment of Cavalry,* enlisted November 1[?]], 1863 at Livingston, Miss. by Capt. Red for 3 years, deserted July 28, 1864, no other records

* The designation of this regiment was changed to the 12th Regiment Mississippi Cavalry March 24, 1865

Compiled Service Records of Confederate Soldiers Who Served in Organizations from the State of Mississippi