“Gettysburg: The Last Invasion,” is a terrific new book by a historian named Allen C. Guelzo, who is a fine writer, a superlative researcher, and a radical thinker. I’ve been reading about the battle practically since it happened, and I doubted that anyone could come up with anything really new, but he has.

Guelzo has drawn a number of conclusions that will infuriate some and enrage others, but among the most startling of his conclusions is this (in my words): The horrendous number of casualties over those three days was caused not by the effectiveness of the rifle musket, but by the poor training (or nonexistent training) of the soldiers involved, the near impossibility of controlling them in any kind of effective fashion, and the epic incompetence of some of the generals involved. It was, he states, an era of combat in which it was still more or less safe to stand erect on the field of battle.

Some of this makes sense. The British used the rifle musket in the Crimean War, a decade before Gettysburg, so what it could do was hardly a mystery. And it’s true that many of the soldiers involved, North and South, were incompetent in its use. After the battle, Union ordnance collected thousands of muskets with multiple charges rammed down their bores, some exploded, some not; in their hysteria, soldiers thought they were firing but weren’t.

Moreover, Guelzo states, the actual rate of fire for a rifle musket was not the three rounds per minute that is usually claimed, but one every four and a half minutes. And as for drawing a bead on an enemy soldier hundreds of yards away, the battlefield was usually so shrouded in smoke that all you could see was the feet of your enemy and muzzle flashes amidst the murk.

Arguing against this is the fact that of all the casualties inflicted in the Civil War, 90 percent (This figure varies somewhat, but 90 percent is a safe average) were caused by musket fire, with artillery, bayonets, and swords doing the rest of the work.

Nor was it safe to remain upright. Officers, through general rank, were supposed to stand, or sit their saddles through a battle or be viewed with contempt. Most of them did, and they were killed in droves. The troops learned very early on that to march toward an objective (as in Pickett’s Charge, or the Union assaults at Fredericksburg and Cold Harbor) was to commit suicide, and if left to their own devices they went forward in rushes, as infantrymen do today. If you were upright, you were dead. Guelzo, I think, underplays the ability of the men who fought there. Early in the war (First Manassas, Antietam) battles were collisions between armed mobs, but by the time of Gettysburg, it was a contest between the hard core of both armies. The soldiers were nearly all veterans and knew what they were about, as did many of their officers.

I’d like to make it perfectly clear that I disagree with Mr. Guelzo on this one point, and who knows, he may be right and not I. Either way, if you’re a Civil War buff, “Gettysburg: the Last Invasion,” should be right at the top of your reading list. It is fresh, insightful, vivid, and will make it plain to you that you would not want the dreams of anyone who survived that battle.