succeed, secede

Succeed or succeed ( suck seed ) means to achieve what was intended, or to arrive at the desired outcome of a plan or project--
If you don't do your schoolwork, you will not succeed.
He worked late every night on order to succeed in achieving the goals he had set for himself.

Secede or secede ( seh seed ) means the declaration of a state or a set of people to separate themselves from their country, and to form their own state or nation--
During the American Civil War, the North refused to acknowledge any right to secede from the union.
When the state of Virginia decided to secede from the union, the western part of the state decided to secede from Virginia, and form its own state, called West Virginia.

Now that you know that, you can say--
"The southern states did not succeed in their plan to secede from the union."

Note--"success" is the noun ( thing or idea ) form of "succeed"--
Work hard, and you will be a success.
"Succession" means a series of things--things that come one after the other, in order--
The project was plagued by a succession of  disasters.
"Succession" is also the term used when a monarch dies or gives up a throne, and is replaced by someone else--
The "Act of Succession" states plainly who will be the next king or queen.
"Secession" is the noun ( thing or idea ) form of  "secede"--
The secession of some of the southern states began the Civil War.