During a recent Baltic Sea exercise by NATO's Standing Mine Countermeasures Group 1, nine of the 26 mine clearing vessels involved, cleared 59 World War II era mines from the coast of Estonia. During World War I and II, some 80,000 naval mines were laid in that area, and the Gulf of Finland in general. Most of the World War I mines were cleared out in the 1920s. But after World War II, the Russians didn't clear all the mines in coastal waters they controlled. Many areas were simply declared "off limits." That saved the Russians a lot of money and effort, especially, with the start of the Cold War in the late 1940s, and renewed thoughts of putting a lot of naval mines in the Gulf of Finland. But now the Cold War is over, the Baltic States (Latvia, Estonia, and Lithuania) are free again (they were taken over by Russia in 1940), and they would like to make their coasts "mine free" (as is the case in Western Europe, which cleared all its mined coasts by the 1950s). So navies of nearby nations are invited in to practice on the sixty year old mines that are still there.