https://www.thegazette.com/art/a-trip-back-in-time-at-the-battle-of-shiloh-iowans-held-the-line/
A Trip Back in Time: At the Battle of Shiloh, Iowans held the line
The battle started with a surprise attack by Confederate soldiers in the early morning of April 6.
Gen. Ulysses S. Grant's Union army had arrived at Pittsburg Landing on the Tennessee River and set up camp on April 5 near Shiloh.
During the first day of the attack, the Union army retreated toward the river. Iowa soldiers formed a defensive line 600 yards along a 'sunken road.” There was a small rise and deep undergrowth to the Iowans' backs.
Heavy fighting occurred along the line for hours that included eight distinct Confederate charges toward the Union line. More than 60 cannons concentrated fire on the Iowa line.
Confederates named the location the Hornet's Nest because so many bullets were being fired that it sounded like a swarm of angry hornets.
As the Iowans held, other Union defenders to Iowa's left and right flank fell back, allowing some 2,000 troops to be captured late in the day. But they had been successful in delaying the Confederates, giving much needed time for Grant to regroup his Union soldiers and ready the entire army for the next day's counterattack, which would win the battle for the North.
More than 13,000 Union soldiers and approximately 10,000 Confederate soldiers were killed, wounded, captured or missing. The combined casualties of 23,000 was far greater than the other key battles earlier in the war.