In a nutshell Pete, weapons delivery systems, especially thermonuclear.
The old superpowers, Russia & the USA are obvious, as are the now emerging superpowers, China & India.
India's 'regional' Global Navigation Satellite System has a footprint that extends 1000 miles (1600 km) beyond its national borders, especially important for them is to reach Islamabad and even southern China.
One of the biggest difficulties Britain faced with its strategic nuclear deterrent was that they were, and still are, manufactured and serviced by the Americans. This is why the UK Got spent vast amounts on developing alternative guidance systems for them, which experts say are a second best. Maybe this is why a paper in the Successor Programme looks at employing Galileo in Trident's replacement.
It is important to remember that the world's first GNSS, GPS, would never have been available to the public were it not for the tragedy of Korean Airline, Flight 007. This the event was one of the most important factors that prompted the Reagan Administration to allow worldwide access to the United States military'sGNSS system, which was classified at the time.
