Usually when it is mis-named or conveniently forgotten.
Take the Parliamentary war, or the Great Rebellion – 1642 to 1651 between the Parliamentarians and the Royalists. This is often referred to as the English Civil War, as if there were no others. But this is wrong, there were others before that.
The death of Henry I’s son, William, in a shipwreck in 1120 certainly led to one which eventually engulfed both Normandy and England.
King Henry later declared his daughter, Matilda, as his heir but when he died in 1135 his nephew, Stephen of Blois, seized the throne. Matilda, who was also the Holy Roman Empress at the time, did not agree and went to war with Stephen, this is known as, ‘The Anarchy’ and lasted until 1153 when Stephen agreed to recognise Matilda’s son, Henry, as his heir, and that is how Henry II came to the throne.
A civil war which lasted 18 years and resulted in thousands of deaths cannot be pushed aside by another, later civil war.
Then there was the War of the Magna Carta. King John was now occupying the throne of England and making such a mess of it, including upsetting the Pope and losing most of England’s possessions over the sea to the French King Philip, II, the English nobility decided to end John’s incompetence by presenting him with a charter to sign, the ‘Magna Carta,’ in 1215.
When John realised that he had signed away many of his king’s, ‘Rights Absolute,’ He reneged on his signing and brought about another civil war which lasted till his death at Newark in October 1216.
So be careful when you refer to, ‘The English Civil War,’ and say which one you mean.