structural:summarization, quality:corruption
Background

From the eighteenth century until the mid twentieth century, the territorial waters of the British Empire, the United States, France and many other nations were three nautical miles (5.6 km) wide. Originally, this was the distance of a cannon shot, hence the portion of an ocean that a sovereign state could defend from shore. However, Iceland claimed two nautical miles (3.7 km), Norway and Sweden claimed four nautical miles (7.4 km), and Spain claimed six nautical miles (11 km) during this period. During incidents such as nuclear weapons testing and fisheries disputes some nations arbitrarily extended their maritime claims to as much as fifty nautical miles (93 km) or even two hundred nautical miles (370 km). Since the late 20th century the "12 mile limit" has become almost universally accepted. The United Kingdom extended its territorial waters from three to twelve nautical miles (5.6 to 22.2 km) in 1987.