But to say that the south was "invaded" by the North, well lets just say that is a bit self serving to the cause.
Once the south seceded the war was on, for all intense and purposes. The location of the War just had to be determined and the North decided first.
Most people forget that it began as entirely a War of Southern Aggression against the Union -- of which the firing on Union forces in Fort Sumter was only the most remembered example.
There were many others, including seizures of Federal properties, captures of Federal forces and Southern military invasions of Union states and territories all around the Confederacy.
These were never intended to be "peaceful secession," but rather were provocations for a glorious Second War of Independence, which would establish the Confederacy as a powerful and respected force in the world.