What battle, other than Gettysburg, is the most significant in the war?

Which battle would you say was the most significant, save Gettysburg, of course. Gettysburg is arguably the turning point and most poignant point of the war. But besides the battle there, which was the most significant in your opinion?

I would say the most significant when the Confederate first pulled the trigger on Fort Sumter. Based on what I have gathered so far, that particular incident blemished the CSA's reputation in the views of the people who did not know what really happened.

If the North were the ones who attacked first, then would you think the CSA would get more supporters from the North? I think because in that particular situation in Fort Sumter, whoever strikes first will be at a disadvantage.

Yeah, I remember the old Revolutionary War saying, "Don't shoot until you see the whites of their eyes."

I think a pivotal battle, or moreover a series of battles, was the defense of Richmond in 1864. Keeping the Feds out was crucial.

I would say the battle of Chickamauga was important;  Chickamauga was the first major Confederate effort to use the "interior lines of the nation" to transport troops between theaters with the aim of achieving a period of numerical superiority and taking the initiative in the hope of gaining decisive results in the West. "The concentration the Confederates achieved at Chickamauga was an opportunity to work within the strategic parameters of Longstreet's Defensive-Offensive theory."It was the Confederates' last realistic chance to take the tactical offense within the context of a strategic defense, and destroy the Union Army of the Cumberland. If a major victory erasing the Union gains of the Tullahoma Campaign and a winning of the strategic initiative could be achieved in late 1863, any threat to Atlanta would be eliminated for the near future. Even more significantly, a major military reversal going into the election year of 1864 could have severely harmed President Lincoln's re-election chances, caused the possible election of Peace Democrat nominee George McClellan as president, and the cessation of the Union war effort to subdue the South