Abstract: A land mine is provided with a pair of nested bowl shaped parts having their respective contacting surfaces arranged for tangential displacement relative to one another, and an actuating device provided in the mine is selectively responsive to such tangential displacement for activating the percussion mechanism in the mine. The actuating device includes a member located in a space provided between the contacting surfaces of the nested parts, and a locking device operates in response to the presence of a predetermined external force to lock such member to one of said parts to cause said member to activate the percussion mechanism upon occurrence of the tangential displacement between the parts. The locking mechanism is responsive to the absence of said predetermined external force for unlocking said member from said part to prevent activation of the percussion mechanism upon occurrence of said tangential displacement between the parts.