164 years ago today: "No terms but unconditional and immediate surrender can be accepted."

In early 1862 the Confederacy’s entire western defense depended on a simple geographic reality: rivers were highways. The Tennessee and Cumberland Rivers ran north into the Ohio River, meaning Union gunboats could sail straight into the Deep South if the entrances weren’t blocked. To stop that, the South built two forts only twelve miles apart - one on each river - forming the center of their defensive line across Kentucky and Tennessee.

Grant aimed directly at that weak point.

At the Battle of Fort Henry, guarding the Tennessee River, the Confederates were already in trouble before the battle began. The fort sat on low ground that flooded after winter rains, leaving many guns unusable and the position exposed to naval fire. On February 6, 1862, Andrew Foote’s ironclads bombarded the fort while Grant’s infantry marched nearby. The gunboats alone forced surrender in barely over an hour; most of the defenders escaped to Fort Donelson.

The Tennessee River was the Confederacy’s back door. With Fort Henry gone, Union forces could steam south into Tennessee and Alabama, bypassing defensive lines entirely. The Confederate western front was no longer a wall, Grant had punched a giant gap through it.

Grant immediately turned east toward the fort that actually held the line together: Fort Donelson, located on the Cumberland River. Donelson protected the direct water route to Nashville and anchored the entire Confederate position in the state. For several bitter winter days the Union army surrounded it. On February 15, the Confederate army launched a powerful breakout attack and opened an escape road, but command confusion halted the retreat. Grant counterattacked, closed the trap, and the next morning demanded “unconditional and immediate surrender.” Around 12,000–15,000 Confederates were captured - an entire army, the first of three Grant would capture intact during the war.

Fort Donelson was the keystone for the Confederates in the Western Theater. Once it fell, the Confederates could no longer defend Nashville or even most of Tennessee. Kentucky became securely Union territory, the Southern defensive line in the West collapsed, and the Union gained permanent river highways for future campaigns deeper into the Confederacy.

Together the battles worked like a one-two punch: Fort Henry opened the rivers, and Fort Donelson forced the Confederacy to abandon an entire region. Overnight, the Union went from stalemate to offensive war in the West and Grant became a national hero.

Thus, "Unconditional Surrender" Grant entered the national consciousness....164 years ago today.