Realizing that he could not defend Richmond forever from the Union's overwhelming numbers and heavy siege artillery and that McClellan's army was divided by the rain-swollen Chickahominy River, Johnston attacked south of the river on May 31 in the Battle of Seven Pines or Fair Oaks. His plan was aggressive, but too complicated for his subordinates to execute correctly, and he failed to ensure they understood his orders in detail or to supervise them closely. The battle was tactically inconclusive, but it stopped McClellan's advance on the city and would turn out to be the high-water mark of his invasion. More significant, however, was that Johnston was wounded in his shoulder and chest by an artillery shell fragment near the end of the first day of the battle. G.W. Smith commanded the army during the second day of the battle, before Davis quickly turned over command to the more aggressive Robert E. Lee, who would lead the Army of Northern Virginia for the rest of the war. Lee began by driving McClellan from the Peninsula during the Seven Days Battles of late June and beating a Union army a second time near Bull Run in August.