I can not find the reference i used before but here it is repeated time after time.
"The South could 'win' the war by not losing," writes McPherson, but "the North could win only by winning."
Although outnumbered and lacking the industrial resources of the North, the Confederacy was not without advantages of its own. It was vast—750,000 square miles the Federals would have to invade and conquer. "Thus space was all in favour of the South; even should the enemy overrun her border, her principal cities, few in number, were far removed from the hostile bases, and the important railway junctions were perfectly secure from sudden attack. And space, especially when means of communication are scanty, and the country affords few supplies, is the greatest of all obstacles."
https://www.historyonthenet.com/could-the-south-have-won-the-civil-war
To accomplish their aims, the Union would have to be aggressive and fight to win.They would have to invade, conquer and occupy the South .
The Confederacy –fighting a defensive war –would not have to win to achieve its aims of national sovereignty; it just could not lose .
https://www.phoenix.k12.or.us/cms/lib/OR50000021/Centricity/Domain/1172/ush Civil War.pdf
The South also proved to be very resourceful. By the end of the war, it had established armories and foundries [such as Selma] in several states. They built huge gunpowder mills and melted down thousands of church and plantation bells for bronze to build cannon.
The South's greatest strength lay in the fact that it was fighting on the defensive in its own territory. Familiar with the landscape, Southerners could harass Northern invaders. [as long as they were drawn away from the borders]
The military and political objectives of the Union were much more difficult to accomplish. The Union had to
invade, conquer, and occupy the South.
http://www.ushistory.org/us/33b.asp
Davis was argued to have better served the cause by writing off large portions of the Confederacy's scattered territory which would enable him to focus his armies around a few key areas important to the South's survival. It has even been suggested conventional warfare should have been replaced with guerrilla warfare on Union occupation forces .
For the union a massive area of the Confederate States needed to be conquered and occupied, preferably
the size of the whole of Western Europe.
http://www.historyisnowmagazine.com...e-confederate-south-have-won-the-us-civil-war