Question: Who did the general in the Union Army during the American Civil War pave the way for the surrender of Fort Donelson, who later became the 18th President of the United States?

Context paragraphs:
Daniel Smith Donelson: Daniel Smith Donelson (June 23, 1801 – April 17, 1863) was a Tennessee politician and soldier.  The historic river-port of Fort Donelson was named for him as a Brigadier in the Tennessee militia, early in the American Civil War, in which he went on to serve as a Confederate general, notably at Perryville and Stones River.  He was the nephew of America's seventh president, Andrew Jackson.

Fort Donelson: Fort Donelson was a fortress built by the Confederacy during the American Civil War to control the Cumberland River leading to the heart of Tennessee, and the heart of the Confederacy.  The fort was named after Confederate general Daniel S. Donelson.

Ulysses S. Grant: Ulysses S. Grant, born Hiram Ulysses Grant , (April 27, 1822 – July 23, 1885) was the Commanding General of the United States Army at the end of the American Civil War and later the 18th President of the United States from 1869 to 1877.  As Commanding General, Grant worked closely with President Abraham Lincoln to lead the Union Army to victory over the Confederacy in the Civil War.  Supported by Congress, Grant implemented Reconstruction, often at odds with President Andrew Johnson.  Twice elected president, Grant led the Republicans in their effort to remove the vestiges of Confederate nationalism and slavery, protect African-American citizenship, and support economic prosperity.  Although his presidency has often been criticized for multiple administration scandals and for his failure to alleviate the economic depression following the Panic of 1873, he is regarded as a President who performed relatively well in the context of his time and pursued justice for all.

John Pope Cook: John Pope Cook (June 12, 1825 – October 13, 1910) was an Illinois politician and a general in the Union Army during the American Civil War.  He served in the Western Theater and played a prominent role in securing the Union victory at the Battle of Fort Donelson, helping to force the surrender of the defenders.

Isham N. Haynie: Isham Nicholas Haynie was a lawyer, politician, soldier and officer in the Union Army during the American Civil War.  He was colonel of the 48th Illinois Volunteer Infantry Regiment at the battles of Fort Donelson and Shiloh.

Fort Donelson National Battlefield: Fort Donelson National Battlefield preserves Fort Donelson and Fort Heiman, two sites of the American Civil War Forts Henry and Donelson Campaign, in which Union Army Brigadier General Ulysses S. Grant and Flag Officer Andrew Hull Foote captured three Confederate forts and opened two rivers, the Tennessee River and the Cumberland River, to control by the Union Navy.  The commanders received national recognition for their victories in February 1862, as they were the first major Union successes of the war.  The capture of Fort Donelson and its garrison by the Union led to the capture of Tennessee's capital and industrial center, Nashville, which remained in Union hands from February 25, 1862 until the end of the war, and gave the Union effective control over much of Tennessee.  This struck a major blow to the Confederacy early in the war.

James M. Tuttle: James Madison Tuttle (September 24, 1823 – October 24, 1892) was a soldier, businessman, and politician from the state of Iowa who served as a general in the Union Army during the American Civil War.  He commanded a brigade and then a division in the Army of the Tennessee in several campaigns in the Western Theater of operations.  He led the first Union troops that entered the enemy-held Fort Donelson in 1862, paving the way for the fort's subsequent surrender to Ulysses S. Grant and opening the Cumberland River as an avenue of invasion of the South.

Palmyra, Tennessee: Palmyra is an unincorporated community in Montgomery County, Tennessee.  It is located along State Route 149, southwest of Clarksville.  The town had its own post office until around 2010 when the post office was closed and mail service began to be handled out of nearby Clarksville.  The zip code for Palmyra is 37142.  Palmyra has a rich Civil War history with Major General Joseph Wheeler of the Confederate army took position on the Cumberland River in late January 1863.  His plan was to disrupt Union ships going to Fort Donelson at Dover, a few miles west of Palmyra.  Aware of Wheeler's intentions, the Union did not send any ships up or down the river, forcing Wheeler to attack Fort Donelson with his cavalry division.  Wheeler was unable to take Fort Donelson and had to retreat after sustaining heavy losses.

Battle of Fort Donelson: The Battle of Fort Donelson was fought from February 12–16, 1862, in the Western Theater of the American Civil War.  The Union capture of the Confederate fort near the Tennessee–Kentucky border opened the Cumberland River, an important avenue for the invasion of the South.  The Union's success also elevated Brig. Gen. Ulysses S. Grant from an obscure and largely unproven leader to the rank of major general, and earned him the nickname of "Unconditional Surrender" Grant.

Susan Cox (Civil War nurse): Susan Cox was a Union nurse during the American Civil War.  Cox enlisted in October 1862, in Knox County, Illinois.  She served with the 83rd Illinois Infantry throughout her career, serving at Fort Henry, Fort Donelson, and Clarksville.  Because Cox remained with the same regiment, and spent much of her time with them at Fort Donelson, her experiences weren't as varied as the stories of some Civil War nurses.  At Fort Donelson, Cox witnessed daily fight with the enemy.  This work exposed Cox to enemy fire and camp life difficulties as she cared for the ailing soldiers.  Cox's husband was also part of the infantry; one day, as Cox was following her husband and his company up the Cumberland River, a skirmish broke out.  Cox also witnessed a man publicly executed for desertion.  After many challenging experiences, Cox's service ended June 1864.

Supporting paragraphs: James M. Tuttle Ulysses S. Grant
Answer: Ulysses S. Grant