On February 16, 1862, Confederate forces holding Fort Donelson in Tennessee surrendered to Union troops. U. S. Grant’s army captured 12,000 Confederate soldiers. Grant’s terms of surrender were suggested by General Charles F. Smith. Grant agreed with Smith’s recommendation and earned the moniker “Unconditional Surrender.”
You can learn the story in my biography of Major General Charles F. Smith, Teacher of Civil War Generals. The e-book is available on Amazon at https://www.amazon.com/Teacher-Civil-War-Generals-Commandant-ebook/dp/B0134XZD5G.
Allen Mesch 