When J.E.B. Stuart fired off those cannons to signal Lee, the alarm was instantly raised.

Brig. General David McMurtrie Gregg brought his men – two brigades under the command of Col. John McIntosh, and newly-appointed Brig. General George A. Custer – up the Low Dutch Road to meet the threat to the Union rear. By this time 150 years ago, they were in position to do something.

It began with an artillery duel. The well-trained Union gunners were able to overpower Stuart’s horse artillery. J.E.B. would need another trick to get past them.

He decided on a flanking movement, but he was blocked by troopers from the 5th Michigan Cavalry. Just as he had them breaking, the 7th Michigan counter-attacked, personally led by General Custer himself.

Fighting would swirl around these fields for less than an hour. Charge and counter-charge happened again, and again General Custer and his Michigan boys made the difference.

The struggle came to a head when Col. McIntosh’s brigade was able to flank the Confederates, wounding Confederate Brig. General Wade Hampton in the process. In mass confusion, and nearly surrounded, the Rebel horsemen had no choice but to retreat.

While relatively light on casualties for both sides, this little-mentioned action represented another step up for the Union cavalry, and another missed opportunity for J.E.B. Stuart and the Confederates. The tides were slowly turning.

In preparation for the infantry assault against the center of the Union line on Cemetery Ridge, General Lee ordered a massive artillery barrage. It would be the largest of the war.

Nearly 150 guns from all three Confederate corps would participate. With any luck, the concentrated fire of all these weapons would damage the Union guns and cause the infantry to flee in panic. It would have to be perfectly executed, as the Confederates had little ammunition to spare.

Lee gave Longstreet overall command of the attack, and he assigned the artillery portion to Col. E. Porter Alexander, the I Corps artillery chief. Alexander was a brilliant up-and-comer in the Army of Northern Virginia, and had the ability to look at situations very objectively. Before the day was out, he’d be placed in a very awkward situation.

150 years ago right now, the firing commenced. It didn’t take long for the Union guns to respond. With both sides blasting away, the area around Gettysburg became a loud, smokey mess – so loud in fact that the barrage was heard as far away as Washington, DC and Pittsburgh, PA. It was impossible to see what the enemy was doing through all of that, and whether your own fire was having an effect.

Despite this fog of war, it also didn’t take long for the Brig. General Henry Hunt – Chief of Artillery for the Army of the Potomac (and the man who literally wrote the book on artillery before the war) – to recognize that this wasn’t merely an artillerist’s duel. This was the clear prelude to an infantry assault. The Rebels would charge across those fields as soon as they thought they’d inflicted enough damage – Hunt was sure of it. He ran around to each of his battery commanders and told them to slow down. The infantry commanders were furious – the artillery should be returning fire vigorously!

There was a method to Hunt’s seeming madness. Not only would slowing down conserve ammunition for the coming infantry attack, it would lull the Confederates into thinking that there was a steadily decreasing number of guns firing back at them – perhaps they were damaging the Union defenses!

After an hour and a half of this, the Confederates were running low on ordnance, and were taking too much damage from the Union return fire. The Rebel artillery was going to be forced to stop soon.

While the fighting resumed on Culp’s Hill early in the morning, General Lee came up with his strategy for the day’s action.

Originally, he wanted to repeat the attacks on the left and right from yesterday, hoping that more ground could be gained this time. Lt. General Longstreet convinced him that the Union left was well-situated on the ridges south of town. Lee changed his strategy – he would launch an attack that would become famous against the center of the Union line, and his cavalry would have a part to play this time.

The Confederate artillery would break up the Union defenses, the infantry would push the Yankees off Cemetery Ridge, and the cavalry would be waiting to mop up the remains.

J.E.B. Stuart was to go around the Union right, probing for the rear of the enemy. Once he found it, he should signal General Lee to let him know that the cavalry was in position.

150 years ago right now, four cannons fired off on Cress Ridge near the Rummel Farm – one blast in each compass direction. This was the signal. Unfortunately for Maj. General Stuart, his commander wasn’t the only person to hear it.

Federal artillery on Powers Hill and along the Baltimore Pike, opened fire on the Confederates occupying the lower portion of Culp’s Hill, 150 years ago right now.

During the night, both sides had reinforced their lines, though the Union boys were in a much better position. For the next 6 hours, fighting would rage all along the wooded hillside. It was too loud to effectively convey orders to the men. Thick black powder smoke added to the pre-dawn darkness to create a throughly confusing situation – especially for the attacking Confederates.

The southerners made a few more attempts to take the hill, and were repulsed each time. There was even some Maryland on Maryland fighting (complete with a few cousins fighting each other) – the only instance of a State having men on both sides of a fight at Gettysburg.

In the end, the Rebels couldn’t take any more ground, and the Yankees couldn’t completely drive them off. Both lines essentially returned to their original positions by about 10:30am.

Even though the main part of the fighting had ended, the close proximity of the two armies on Culp’s Hill led to a few volleys being blindly fired into the dark by both sides. 150 years ago right now, one such short firefight broke out. There was another one about an hour later around 2:00am, and one more right before the battle resumed in earnest around 4:00am.

Sometime this evening, Maj. General Meade called a council of war with his senior staff and the corps commanders. It took place sometime after the fighting on East Cemetery Hill died down.

So probably about 150 years ago right now, the generals met at Meade’s headquarters in the Leister house. Meade had three questions for the commanders to consider, which were essentially these:

1. Should we stay here, or move back closer to our supply base in Westminster?
2. If we stay, should we attack, or wait for the Confederates to?
3. If we wait for an attack, how long should we?

The consensus was for the army to remain more-or-less in their current location, and wait for the Rebels to come to them. Meade was happy with that decision.

The very fact that Meade left the issue open to a committee of the other generals led to criticism after the battle. There were some who felt that this was Meade attempting to avoid responsibility for the battle if things had gone wrong. Some of the generals accused Meade of secretly wanting to retreat to his Pipe Creek Line (with the implication that this would have been less-than-honorable).

This was just Meade’s style, and it was understandable – especially given how intense his first week on the job had been.

As part of his demonstration against the Union right, Lt. General Ewell ordered an assault against East Cemetery Hill. 150 years ago right now, that attack began.

Brig. General Harry Hays’ Louisiana Tigers and Col. Isaac Avery’s (temporarily replacing the wounded Brig. General Robert Hoke) North Carolinians would make the charge across the fields and up the hill. The Union line was not well-positioned in this sector – there was no clear military crest on the east slope of Cemetery Hill, and the men who were holding this position were the shattered remains of the less-than-reliable XI Corps.

Though the infantry was in a tough spot, the Union artillery was well-placed. Four batteries were in place, with another to the right on a small hill between Cemetery and Culp’s that would come to be called Steven’s Knoll.

With daylight fading, the Confederates came on strong. Within 30 minutes, they had dislodged the Yankee defenders and sent them fleeing up the hill. It proved impossible to follow-up on this success, though.

Only a few of the Rebels made it up the hill, and they were able to temporarily seize a few of the cannons, but Cemetery Hill, being near the center of the Union position had too many troops readily available as reinforcements for the Confederate foothold to last. Hays’ and Avery’s men were beaten back in short order. Cemetery Hill was quiet – and securely in Union hands – by 9:00pm.

As the Confederates who broke through the III Corps‘ line pushed across the open fields toward Cemetery Ridge, a huge hole had opened up on the right flank of the II Corps. Troops from the III Corps were fleeing to the rear through this hole, and a Confederate brigade under the command of Brig. General Cadmus Wilcox was right behind them.

Maj. General Hancock was desperate to plug the gap. He looked around for a unit – any unit – that could delay the Confederate advance long enough to form a defensive line. The only men he could find were 8 companies of the 1st Minnesota Infantry.

The regiment had been split up to perform different duties across the Union line, and while the bulk of the men were at this point, it wasn’t the whole regiment – only 262 men. Maj. General Hancock rode up to Col. William Colville, pointed at the approaching Confederate brigade of 1,721 men, and said “Colonel, go take those colors!”.

Against worse than 6-to-1 odds, the men of the 1st Minnesota charged down the gentle slope of Cemetery Ridge, 150 years ago right now. After less than 10 minutes of fighting – enough to allow the Union commanders to rally a defensive line behind them – the Minnesotans fell back.

There were only 47 of them left. The 262 men of the 1st Minnesota had taken 215 casualties – an 82% casualty rate. This is the highest percentage of casualties suffered by a surviving unit in American history.

The Confederate attack on the Union left was over.

With the attack against the Union left, most of the troops on Culp’s Hill had been pulled off to reinforce other sectors. Only the brigade of Brig. General George Greene, the oldest general on the field, remained.

Greene’s 1,421 men were as well-prepared as they could be under the circumstances. Brig. General Greene was a West Point-trained engineer who believed in the power of defensive structures. His men had spent the day building small trenches and breastworks – digging in for a potential Confederate attack. It is fortuitous for the Union cause that these were the men who were left on Culp’s Hill.

The Confederates’ original plan for the day involved Lt. General Richard Ewell’s Corps creating a diversion by attacking Culp’s and Cemetery Hills while the main attack was being executed by Lt. General Longstreet on the Union left. This would keep the troops on the Union right occupied so that they couldn’t be used (like they were) to reinforce the left. Ewell was supposed to begin his action as soon as he heard Longstreet’s attack. The combination of Longstreet’s delay in movement, and a phenomenon known as “acoustic shadows“, led to Ewell never getting the signal to go.

Finally, about 150 years ago right now, Ewell started his attack on Culp’s Hill. He was running out of daylight, so the move was risky, but he went ahead with it anyway. Greene’s small brigade would face off against almost a full division – 3 brigades of Confederate infantry. They were outnumbered more than 3-to-1.

The breastworks proved to be a big advantage for the Yankees. Because of those, Greene was able to hold the crest of the hill. Despite a few assorted reinforcements, from other brigades coming to their aide, the Federals lost control of the southern, lower portion of Culp’s Hill.

In two hours of combat, the Confederates had beaten back their adversaries, but couldn’t totally push them off. If the Confederates had properly scouted the area, they’d have known that the Baltimore Pike – the main supply line for the Union army – was within easy striking distance of their new position. With that intelligence, they could have caused serious problems for General Meade. As it was, they were content to hold their newly-gained position.

It was only a matter of time before the battle would reach Sickles’ salient at the Peach Orchard. The main weakness of a salient is that it can be attacked from two sides. That’s just what’s about the happen.

150 years ago right now, the division of Maj. General Lafayette McLaws – especially the brigades of Brig. General Joseph Kershaw and Brig. General William Barksdale – will come across the Emmitsburg Road, and strike the men of Brig. General Charles Graham. Within an hour of the first contact, the Union troops occupying the exposed position will be forced to withdraw in a somewhat less-than-organized fashion. The rest of Brig. General Andrew Humphreys’ division, holding the line going north along the Emmitsburg Road, will have to abandon their position a little after 7:00pm, too.

For the moment anyway, the Confederates will have a clear route to the Union rear. They’ll soon be within range to flank the II Corps. Someone on the Union side needs to take control here.