In March, one of the Western world’s worst nightmares came true. The United States and South Korea began their annual joint military exercise, code-named “Foal Eagle,” involving over 10,000 American soldiers and an additional 200,000 South Korean troops.One of the scenarios played out during the drill, simulating a potential military conflict between the two sides of the peninsula in the event that longtime North Korean leader Kim Jong II dies and his son Kim Jong Un is incapable of establishing control, seemed more than realistic.Toward the end of the exercise, global positioning systems started to fail, particularly in areas such as the capital, Seoul and the city of Paju. Most affected were US Tomahawk cruise missiles as well as Joint Direct Attack Munition (JDAM) bomb kits, which are supposed to turn regular bombs into smart bombs and accurate satellite-guided weapons.After a short investigation, South Korean intelligence discovered that North Korea had activated two different systems to jam the satellite signal. The first was a vehicle-mounted device North Korea had purchased from Russia in the early 2000s, which is believed to be capable of jamming GPS signals from 50 to 100 km. away.The second system was a spinoff and upgrade of the Russian system manufactured domestically in North Korea that is believed to cost less but has the ability to jam GPS reception within a radius of 400 km.Israel, which for years has feared and prepared for the possibility that in a future conflict with Hezbollah in Lebanon, Hamas in the Gaza Strip, Syria or Iran, its GPS systems will fail, followed these developments closely. The Israel Defense Forces has already considered the possibility that North Korea has sold its GPS jamming system to Middle East countries including Lebanon, Syria and Iran.Just last month, Russia announced that it had sold a series of advanced radar jammers to Iran. Called Avtobaza, the electronic intelligence system might also be able to jam GPS-guided platforms and munitions.“We are preparing and expect that this will be a challenge we will have to deal with in a future war,” a senior IDF officer explained recently. “Our enemies are also building up capabilities.”The ability to jam GPS systems has been a taboo subject within the Israeli defense establishment for years, but with a new conflict looming on the horizon – possibly following an Israeli strike against Iran’s nuclear facilities – there is no ignoring the likelihood that in a future war Israeli smart bombs will be rendered satellite-less.The development of GPS began in the 1970s by the Pentagon and today consists of two dozen satellites that provide global coverage for receivers to determine their precise location within a few meters.The satellites revolve around the earth at an altitude of 20,000 km. and complete one orbit roughly every 12 hours.Over the years, GPS has become an integral part of civilian life and not just of the military. It is used by ships to navigate at sea, by cars to travel by land and by the civil aviation industry as well. Most cellular phones come with GPS chips and its capabilities are often taken for granted.The IDF took its first major step into the world of GPS in 2000 when it became the first foreign customer outside of the US to receive JDAM kits. These were fitted onto 2,000-pound Mk-84 bombs, turning them into precision satellite-guided smart bombs.JDAMs enable Israel Air Force pilots to launch bombs from a standoff position without needing to fly directly over targets where they could be threatened by enemy air defense missile systems.An example of how importance JDAMs are for Israel was provided during Operation Cast Lead in the Gaza Strip almost three years ago. Out of all the bombs dropped, 81 percent were smart bombs, the largest percentage of precision guided weapons ever used in conflict anywhere in the world.But with the reliance come the risks, as jamming systems are more easily available today on the open market. There is also the lingering fear that one day – possibly to prevent Israel from taking military action – the US will shut down the GPS satellites.Maj.-Gen. (res.) Eitan Ben-Eliyahu was commander of the IAF when Israel placed its first order of JDAM kits.“I pushed very hard for the JDAMs since I understood that they were going to provide us with new capabilities that would change the way we operate,” he said. “There are potential problems but when calculating the risks together with the benefits, it is definitely worth relying on such systems.”Israel’s doesn’t just rely on GPS in the air. Take navigation for ground forces as an example. In today’s IDF, Merkava tanks, Namer armored personnel carriers and artillery howitzers are all connected to the Tzayad Digital Army Program (DAP), which shows the position of all friendly and enemy forces.“If a country doesn’t take any precautions to protect GPS then it will be in trouble, since jammers are something that will likely be on a future battlefield,” explained Nir Lavi, director of marketing at Rokar, a Jerusalem-company based that has developed technology to make GPS systems immune to jamming.According to David Last, a former president of the Royal Institute of Navigation and a GPS consultant to the British government, Hezbollah could theoretically place a special radio transmitter on an elevated surface – like a tall mountain in southern Lebanon – and potentially block Israeli GPS from working within a radius of several kilometers.“It takes so little jamming to remove GPS and to jam over a very considerable area – it only requires a radio transmitter that is portable and is easily obtained. If you place it in an elevated location, you can cover a large area,” Last said.Due to the risks, the IDF has been working to develop backup systems for weapons and vehicles that depend on GPS for navigation.If the American GPS satellites are not available, Israel could potentially link up to alternative satellite navigation systems that are under development and will be operational in the near future in the European Union and Russia.Another possibility is for Israel to launch its own satellites. Rafael, a leading Israeli defense company, is developing a capability to launch micro satellites from F-15 fighter jets.The main alternative today to satellite guidance is the Inertial Navigation System (INS), which uses a computer with motion and rotation sensors to calculate the location of the receiver based on the speed, velocity and direction in which it is traveling. In other words, the INS knows what the starting point is and calculates what it will take to get to the target.The problem is that navigation systems based on INS tend to be less accurate, with a steady deviation of 0.8 miles (1.3 km.) per flight hour. INS also costs more than GPS and can reach $10,000 per system.Another possibility is the installation of alternative guidance systems, such as lasers or video guidance, on bombs. One bomb, called Spice, can hit targets either by using GPS navigation or alternatively by using a specially-designed scene-matching guidance system with electro-optical sensor in the weapon's nose.The scene-matching system allows the IAF to feed satellite and aerial footage of up to 100 different targets into the system and then, when in flight, to select a target. The missile starts flying toward the target and scans the topography in comparison to the footage it was fed until it finds what it is looking for.Israel’s GPS navigation systems have yet to really be tested by enemy jamming attempts on the battlefield. But as the IDF hooks more of its units and assets up to networks and becomes more dependent on smart command-and-control systems, it cannot overlook the need for a strong defense. Otherwise it could get jammed.