James Longstreet fought in most of the major campaigns of the Army of the Northern Virginia. He commanded the First Corps, which was more than half of the Army of Northern Virginia. The I Corps was arguably better than the II Corps, which was commanded by the better known "Stonewall" Jackson. Longstreet was the premier Corps Commander of the whole war, on either side. Though he was a figure of controversy, Lee called him "My Old War-Horse" and there is no doubt he held the respect of his Commander and all the troops he led.
Photos from chapters.ausa.org, sonofthesouth.net


Above: Stonewall Jackson (left) , Robert E. Lee (right)
Longstreet started the war as a Lt. Colonel of the infantry. He fought valiantly in the first battle of the war, Manassas (or Bull Run). At the Battle of Seven Pines he made many honest mistakes, but he did not make many after and redeemed himself later. The mistakes at Seven Pines were probably bigger than the mistakes he was accused of at Gettysburg. After fighting well in the 7 Days' Battle he was given command of half of the Army of Northern Virginia. During these campaigns Longstreet became very popular with his troops. His aide Thomas Goree said "Longstreet is one of the kindest best hearted men I ever knew." The troops held a deep respect for their commander.
"If you put every man now on the other side of the Potomac... I will kill them all before they reach my line."-James Longstreet
Above: James Longstreet from Sonofthesouth.net
As for the controversial Battle of Gettysburg, Longstreet voiced objections to it. Previously, Longstreet opposed the invasion of Pennsylvania, and was proved to be right. Longstreet wanted to use the tactical defensive, like at Fredericksburg. He opposed infantry charges and valued life; he wanted the enemy to come to him. The charges made later by critics that Longstreet was slow was also absurd, the reason why he was late in attacking was because of taking a wrong path. The blame should go to Robert E. Lee, who made many mistakes, and openly admitted it. On the third day, Longstreet oversaw the disastrous infantry charge by Pickett (Pickett's Charge) who lost more than 60% of his division. Longstreet was against a charge, but Lee was set to make Pickett's fresh troops make a charge. Longstreet did not do much wrong at Gettysburg, though blamed for losing the battle (and consequently the war) by bitter ex-confederates after the war.
"Ah! Here is Longstreet; here's my old war-horse! Let us hear what he has to say." - Robert E. Lee
Above : A photo of Gettysburg by Alexander Gardner
Later in the war, Longstreet was wounded at the Battle of Wilderness accidentally by his own troops (The same place Stonewall Jackson was shot). Longstreet would return and serve with Lee until Appomattox.