Vastaisku

Vastaisku is a Finnish term meaning counterattack. It describes a planned and executed response aimed at regaining the initiative after the opponent has attacked or penetrated a defense. In military doctrine, a vastaisku is typically a coordinated operation that uses reserves, surprise, and firepower to shift momentum, often launched after securing sufficient intelligence and favorable dispositions. It may be mounted to halt an advance, retake lost ground, or prevent the enemy from consolidating gains. Successful vastaiskut depend on timing, preparation, and integration of maneuvers with artillery, air support, and logistics, while minimizing exposure to counterattack.

Historically, many Finnish defense writings emphasize rapid and decisive counterattacks as a core element of deterrence and defense along the border. The concept is parallel to the general military term counterattack or counteroffensive in other languages, and can be applied across arms domains, including ground, air, and naval operations.

In civilian usage, the term is sometimes adopted metaphorically to describe a rapid, strategic response to a setback in politics, business, or sports, though this usage is less formal.