Although I agree that slavery was a prime issue that contributed to the outbreak of the Civil War, I believe that today's revisionist history has muddied the waters concerning this question. It is true that the Southern states wanted to keep slavery alive as long as possible, and the election of Abraham Lincoln seemed to be another step in this direction. However, the Southern states seceded because they no longer believed that the Federal government was giving them adequate voice in national matters. They organized their armies to protect their borders only after the Federal armies began to invade their homeland. No doubt the Confederate States would have preferred to live peacefully and not go to war, instead simply maintaining the status quo of life as it was in 1860.
Lincoln's primary goal was not to free the slaves; he originally had no intention of emancipating them during his first term. His goal following the secession of the Southern states was to RESTORE THE UNION and reclaim stolen Federal lands. He assumed correctly that only force would achieve this goal. He waited until after the Battle of Antietam (a strategic Union victory) to declare amnesty for all slaves in the South because he only then believed that the war could be won. His Emancipation Proclamation would have had little effect in the South before this time since the Confederate forces had successfully defended their borders. When the invasion of Maryland failed and Lee's defeated (but not yet beaten) army returned home, Lincoln knew it was the time for his momentous decision.
Very few of the more than one-half million soldiers who died during the war chose to give up their lives simply in order to free the slaves in the South. Many men joined both armies for what they thought would be a great adventure and a patriotic duty. Southerners chose to fight because an enemy had invaded their homeland. Northern men were less committed to fight than their counterparts, and there was a strong movement in the U.S. to end the war and restore peace while living as separate nations. Lincoln, of course, would have none of this, and his strong resolve to return the Southern states to the Union was certainly the single most important issue of the Civil War.