A mission or military operation undertaken in response to or in opposition to an enemy's mission.
From counter- (opposing) + mission (from Latin missio, 'a sending forth'). Used primarily in military and intelligence contexts to describe responsive operations.
When a country gets intelligence that another nation is planning a covert operation, their countermission might be equally covert—creating a hidden battle of strategies that the public never sees.
Complete word intelligence in one call. Free tier — 50 lookups/day.