150 years ago today, the first day of Gettysburg, was a day of confusion.

Just three days earlier, the Union army had been completely reorganized under a new leader, George Gordon Meade. Just two days earlier, Robert E. Lee had realized very late that Meade’s army was approaching his own forces as they marched north through Pennsylvania. And just the day before, as the two armies started coming into contact with each other, Lee wheeled to the southeast to attack his new opponent.

On that July 1st morning, Union cavalry approached the advancing enemy, dismounted, and attempted to slow them down. Soon after, an entire Union infantry corps arrived in support, led by the north’s best general, John Reynolds. But within an hour, Reynolds was shot and killed as he was directing the placement of his guns. The northern resistance quickly collapsed, and they had to retreat and reorganize, while the southerners surged forward, chasing them across a series of wooded ridges and right back into the town itself.

Throughout the day portions of the two armies kept arriving from various directions. By the afternoon about a quarter of Meade’s men, and a third of Lee’s men, had joined the scattered fighting. There were skirmishes, pitched battles, cannon fire, sniping, noise, smoke, casualties, prisoner-taking, fear, exhilaration. Above all, there was confusion, as the confederates kept pressing forward and Union defenses kept collapsing.

Meade was in trouble. It was his fourth day on the job, his best officer was dead, and now his army was on the run. So he turned to the man he trusted most: Winfield Scott Hancock. Though outranked by several other union officers, Hancock was ordered to ride forward to take command of the field and assess the situation. He arrived at the front to find that the Union army had lost the town and was now streaming south out of Gettysburg, disheartened and disorganized. Some of Hancock’s beleaguered men had instinctively collected on a line of high ground that offered a clear, unbroken view to the west. Hancock said to the senior officer present, “I think this the strongest position by nature upon which to fight a battle that I ever saw.” The word quickly spread that Hancock had taken charge, and that he had given the order to stand and fight. Union forces rallied to his position, and quickly reorganized themselves all along what is now known as Cemetery Ridge. Tens of thousands of men would arrive throughout the night.

Day 1 ended as Hancock looked west for the approach of Robert E. Lee. “Very well, sir,” he said, “I select this as the battlefield”…