Simplify the following text for a Grade 13 native English-speaking person.
Original: The Battle of Marion ( December 17 â `` December 18 , 1864 ) was a military engagement in the American Civil War that occurred when Major General George Stoneman , commander of the Union Army in Kentucky and Tennessee , raided Southwestern Virginia .
Simplified: The Battle of Marion ( December 17 -- 18 , 1864 ) was a military engagement fought between units of the Union Army and the Confederate Army during the American Civil War near the town of Marion , Virginia .