The Battle of Gettysburg was the highlight of Greene's military career.
On July 2, 1863, Maj.
Gen. George G. Meade shifted almost the entire XII Corps from the Union right to strengthen the left flank, which was under heavy attack.
Greene's lone brigade of 1,350 New Yorkers (five regiments) was left to defend a one-half-mile line on Culp's Hill when an entire Confederate division attacked.
Fortunately, Greene had previously demonstrated good sense (as befits a civil engineer) by insisting that his troops construct strong field fortifications, despite a lack of interest in doing so from his division commander, Geary, and corps commander, Maj.
Gen. Henry W. Slocum.
In Greene's finest moment of the war, his preparations proved decisive and his brigade held off multiple attacks for hours.
He was active the entire engagement rallying his men to defend their positions in the darkness.
Brig.
Gen. Alpheus Williams, acting corps commander on July 2, commended Greene for his "skill and judgment" in this defense, especially in his using the "advantages" of his position.
Late at night, the rest of the XII Corps returned to Culp's Hill.
The fighting resumed the next morning and raged for over seven hours, but the Union troops held Culp's Hill.
They regained some of the lost ground and thwarted renewed Confederate attacks.
The battle for Culp's Hill included the two oldest generals in each army, Greene at 62 and Brig.
Gen. William "Extra Billy" Smith at 65.

The desperate fighting on the Union right flank was as important as the more famous defense of the Union left flank on July 2, by Col.
Strong Vincent's brigade on Little Round Top.
In fact, given that the Union line was only 400 yards (370 m) from the vital Union supply line on the Baltimore Pike, it can be argued that it was more important.
However, Greene's contribution to this critical battle have never been widely heralded, principally because of a dispute between Meade and Slocum over the filing of their official reports.
But a member of Greene's brigade wrote:
Had the breastworks not been built, and had there only been the thin line of our unprotected brigade, that line must have been swept away like leaves before the wind, by the oncoming of so heavy a mass of troops, and the [Baltimore] pike would have been reached by the enemy.
The Battle of Gettysburg was the highlight of Greene's military career. On July 2, 1863, Maj. Gen. George G. Meade shifted almost the entire XII Corps from the Union right to strengthen the left flank, which was under heavy attack. Greene's lone brigade of 1,350 New Yorkers (five regiments) was left to defend a one-half-mile line on Culp's Hill when an entire Confederate division attacked. Fortunately, Greene had previously demonstrated good sense (as befits a civil engineer) by insisting that his troops construct strong field fortifications, despite a lack of interest in doing so from his division commander, Geary, and corps commander, Maj. Gen. Henry W. Slocum. In Greene's finest moment of the war, his preparations proved decisive and his brigade held off multiple attacks for hours. He was active the entire engagement rallying his men to defend their positions in the darkness. Brig. Gen. Alpheus Williams, acting corps commander on July 2, commended Greene for his "skill and judgment" in this defense, especially in his using the "advantages" of his position. Late at night, the rest of the XII Corps returned to Culp's Hill. The fighting resumed the next morning and raged for over seven hours, but the Union troops held Culp's Hill. They regained some of the lost ground and thwarted renewed Confederate attacks. The battle for Culp's Hill included the two oldest generals in each army, Greene at 62 and Brig. Gen. William "Extra Billy" Smith at 65.
The desperate fighting on the Union right flank was as important as the more famous defense of the Union left flank on July 2, by Col. Strong Vincent's brigade on Little Round Top. In fact, given that the Union line was only 400 yards (370 m) from the vital Union supply line on the Baltimore Pike, it can be argued that it was more important. However, Greene's contribution to this critical battle have never been widely heralded, principally because of a dispute between Meade and Slocum over the filing of their official reports. But a member of Greene's brigade wrote:
Had the breastworks not been built, and had there only been the thin line of our unprotected brigade, that line must have been swept away like leaves before the wind, by the oncoming of so heavy a mass of troops, and the [Baltimore] pike would have been reached by the enemy.
George S. Greene