What does "Copenhagening" mean?

What does the naval term "Copenhagening" mean?

It means catching an enemy fleet in harbour and trying to destroy it in detail before it can operate.

The term has a precise operational meaning rather than serving as a general synonym for coercion. It refers to neutralizing naval forces before they can put to sea or join a wider enemy coalition. The object is to catch a concentrated fleet in harbour and defeat its ships in detail while they remain unable to combine at sea. In this episode, the word captures the preventive logic linking the attack on Copenhagen to a wider category of naval action.