A military operation is an organized effort by a nation's armed forces to achieve a specific goal. A CAMPAIGN is a large-scale military operation that involves a series of coordinated battles or engagements over a period of time. A SIEGE is a prolonged military operation in which enemy forces surround a town or building, cutting off essential supplies, with the aim of compelling the surrender of those inside. A MISSION is a specific task assigned to a military unit or individual, usually involving a particular objective to be achieved within a set period of time.