Cartoon map of the 「Anaconda plan」. A plan from General Winfield Scott to crush the Confederacy, economically.
Breaking the Anaconda! is an event for 
Confederate States of America, that can happen after 
USA has taken the decision The Anaconda Plan.
The decision can be taken by the US once they blockade at least 80% of CSA's ports and gives CSA 0.05 war exhaustion pr. month. This events happens as soon as USA does not uphold the blockade, and it removes the effect of the decision. Alternatively it happens once CSA is at peace.
Once the Anaconda is broken, it is not possible for USA to retake the decision.