A breakout is a military operation to end a situation of investment (being surrounded) by offensive operations that achieve a breakthrough—escape from offensive confinement. It is used in contexts such as this: "The British breakout attempt from Normandy". It is one of four possible outcomes of investment, the others being relief, surrender, or reduction. Overview A breakout is achieved when an invested force launches an attack on the confining enemy forces and achieves a breakthrough, meaning that they successfully occupy positions beyond the original enemy front line and can advance from that position toward an objective or to reunite with friendly forces from which they were separated. To be categorized a breakout, an invested force is not necessarily required to be completely encircled by an enemy force. Rather, they may have their movement partially restricted by a terrain feature or potentially the use of an area denial weapon such as the VX nerve agent. That was the case in 1944 in the Saint Lo Breakout in which a large portion of the force's movement was restricted by water and not in fact by enemy positions. While that may be true of a beachhead, it is not necessarily true of a bridgehead. If the bridge is sufficient in capacity compared to the size of the force and does not significantly restrict its movement, it does not represent a sufficient barrier for the force to be considered encircled. Similarly, open water may not be a barrier in the same right. Consider a small detachment of marines with more than sufficient amphibious transports and a significant military presence at sea, such as the beginning stages of the Gallipoli Campaign of the First World War. Had they evacuated to sea, they would retain a significant military presence, as they were principally a naval military force. Conversely, consider the military evacuation of British troops at Dunkirk during the Second World War. The force clearly was pressed by the enemy, and it broke out but lost their effective strength as a fighting force. It was, at the base of it, a land force escaping, not an amphibious force maneuvering. The key feature is the loss of freedom of maneuver. If a force can easily overcome a terrain feature and maintain its fighting strength, it is not breaking out but maneuvering in the same way that any force would over nonrestrictive terrain. A breakout attempt need not