Final answer:
The fatal charge on the third day at the Battle of Gettysburg led by General Lee was known as Pickett's Charge, resulting in heavy Confederate casualties and marking the last of Lee's invasions into the North.
Step-by-step explanation:
The fatal charge on the third day at the Battle of Gettysburg, ordered by Confederate General Robert E. Lee, is known as Pickett's Charge. On July 3, 1863, around 12,500 Confederate soldiers crossed nearly a mile of open field to attack the Union center on Cemetery Ridge. This assault resulted in devastating casualties, with more than half of the attackers wounded or killed, marking the charge as the "High Watermark of the Confederacy". The significant loss of Confederate forces and the retreat of Lee's army to Virginia signaled a decisive turn in favor of the Union and marked the last time Lee would attempt to invade the North.