First, they didn't have early victories in the West. In the West, the South was getting 3 losses for every victory. And in the East what basically happened is that Jackson and Lee proved to be tactically superior to the Northern commanders they faced in most battles until Meade and then Grant took command in the East.
No, it has nothing to do with being better shots because of squirrel hunting. And there were just as many Union units that were rural, especially Western ones. Nor was it about fighting with more ferocity--that does a tremendous disservice to the Northern soldiers who died in battle. The vast majority of Southern soldiers were not fighting in their state and often expressed contempt for the state they were fighting in.
There is this tremendous mythology that has sprung up about the South and the Civil War. The reality is that if Joe Johnston doesn't arrive by railroad, the North wins First Manassas and probably captures Richmond. Than if Johnston doesn't get wounded (so Lee takes command), McClellan probably takes Richmond.
Both sides were filled with officers who learned how to fight in the Mexican-American war (where the most successful tactic was a quick frontal charge against unrifled muskets). But in the civil war, you had the combination of rifled guns (more accurate and greater distance) plus the minie' ball (more accuracy and distance even still). It meant that the tactics of almost all senior officers were bloody and outdated.
Lee and Jackson were simply far more audacious to the Eastern Theater leaders they faced. But that said, all sides were filled with officers who were fighting with outdated tactics. That is why the casualties were so horrendous. Let me illustrate, in just the first 3 hours of Antietam in only the 1st phase of the battle (The Cornfield, West Woods, East Woods), there were 12,000 casualties. Doesn't sound that bad does it? Adjust it from the population of 1862 to the population of 2008 and that would be the equivalent of the US Army in Iraq suffering 120,000 casualties in 3 hours in a battle. What went on in the Civil War was butchery of the highest kind. What passed for victories were mutually bloody affairs that in many ways reflected poorly on both sides (other than it being a demonstration of immense courage).
Scott--just a few things about your post.
1. The South prepared against "green" troops? Both sides were green. And until Joe Johnston's troops arrived via train, the South was losing First Manassas and McDowell would have had a straight road to Richmond.
2. BOTH sides thought the war would be short. The South didn't even see a need for conscription at the beginning of the war.
3. Yes, the South had a lot of early victories--in the E.AST (as my post noted). That was primarily a function Lee and Jackson versus tactically inferior opponents in the East. But the West was a different story. Here is a nice summary in about 2 sentences of the Civil War in the West from a source other than myself: "Military historian J. F. C. Fuller has described this--the Western Theatre battles--as an immense turning movement, a left wheel that started in Kentucky, headed south down the Mississippi River, and then east through Tennessee, Georgia, and the Carolinas. With the exception of the Battle of Chickamauga and some daring raids by cavalry or guerrilla forces, the four years in the West marked a string of almost continuous defeats for the Confederates; or, at best, tactical draws that eventually turned out to be strategic reversals. And the arguably most successful Union generals of the war (Grant, Thomas, Sherman, and Sheridan) came from this theater, consistently outclassing most of their Confederate opponents (with the possible exception of cavalry commander Nathan Bedford Forrest)." So actually my original post that the South had about 1 victory for every 3 losses in the West was a bit generous?
4. Not respecting the men who fought in this war? Please go back and read my post. There are a number of historians, military tacticians, and any civilian with a brain who walks the ground and envisions the mess of The Cornfield, the Hornet's Nest, or the waves approaching Marye's Heights and asks "how could they make that charge?" The Civil War was fought with outmoded tactics by generals who weren't prepared for the reality of the war and thus asked their men to engage in near suicidal actions. I don't dis-respect the men who fought, I do however have contempt for most of the general officers who continued to order frontal attacks against rifled muskets. Sir Douglas Haig (ie: the Somme) would have been right at home commanding an Army or Corps on either side.