North Korea's failed missile launch overnight has once again highlighted concerns about that country's missile and nuclear weapons programs.
Much is not known about the programs, but there are a number of parameters that officials have assessed or made public.
Here is a guide to some questions you might have about North Korea and those programs.
Who is in charge of North Korea’s military? Kim Jong Un is the 33-year-old "Supreme Leader" of the Democratic People's Republic of Korea, more commonly known as North Korea. He is also the Supreme Commander of the Armed Forces. He inherited his position as North Korea's leader following the death of his father Kim Jong Il in December, 2011. North Korea is the world's only hereditary communist dictatorship: Kim Jong Un's grandfather was the founder of North Korea.
How large is North Korea's military? The Pentagon estimates that North Korea's army has more than 1 million soldiers, making it the fourth largest army in the world. Some 4-5 percent of North Korea's 24 million people serve on active military duty and another 25 to 30 percent of the population serve in some reserve military capacity.
What is the DMZ? DMZ stands for the Demilitarized Zone that divides North Korea and South Korea. The 2.5 mile-wide DMZ stretches for 160 miles along the Korean Peninsula and is a buffer zone created by the 1953 Armistice that halted the Korean War. While the zone itself is demilitarized, the areas beyond it on both sides of the border are some of the most militarized in the world. Panmunjon is the Joint Security Area where occasional meetings are held by representatives of North Korea and the United Nations Command.
Is the North Korean military a threat? Most of North Korea's military equipment dates to the Cold War-era and was obtained from the Soviet Union and China. But the large size of its military poses a continual standing threat to South Korea, since 70 percent of its ground forces half its air and navy forces are stationed within 60 miles of the DMZ. And North Korea has been working for the last decade to develop a nuclear weapons program and long range ballistic missile program.
What is a ballistic missile? A ballistic missile uses propulsion to launch it into an upward trajectory and then falls to earth on its own towards a target using gravity. The use of ballistic to describe these missiles comes from the physics term "ballistic trajectory" that describes the boosted launch and fall to earth by gravity.
How far can North Korea’s missiles travel? North Korea has intermediate-range missiles that can travel more than 2,000 miles. However, its successful missile tests of these Musudan and KN-11 missiles have not traveled that far when launched. The Unha rocket is a satellite launch program that early last year successfully placed a satellite in orbit. U.S. officials have said the Unha testing program is really a cover for North Korea to develop long range missiles under the guise of a civilian program.
How many missiles does North Korea possess? The Pentagon's estimates that North Korea has about 200 launchers that can be used to fire short- and medium-range ballistic missiles. It estimates North Korea has fewer than 100 launchers for various versions of the SCUD missile that can travel from 200 to 600 miles. And fewer than 50 launchers for its medium range No Dong missile that can travel 800 miles. The Pentagon estimates North Korea also has fewer than 50 launchers for intermediate range missiles like the Musudan and KN-11 that can travel up to 2,000 miles.
Can North Korean missiles reach the United States? No. North Korea's intermediate-range missiles do not have the capability of reaching Hawaii or Alaska. However, if reconfigured for a different trajectory it is possible for the Unha rocket to come close to those states.
What does ICBM stand for? ICBM stands for intercontinental ballistic missile, a guided missile capable of traveling more than 3,418 miles to deliver a nuclear warhead. ICBM's are usually multi-stage rockets used to boost a payload into a sub-orbital trajectory. At that point the nuclear warhead inside the payload would re-enter the atmosphere using a guidance system to strike its intended target.
Does North Korea have an ICBM? In early January, Kim Jong Un claimed that North Korea was close to testing an ICBM. However, there have been no indications of such a launch taking place. Two successful Unha satellite launches would indicate that North Korea has made progress in a multi-stage delivery system.
Why are North Korea's missile launches a provocation? Over the past decade North Korea has continued to conduct missile tests and launches in defiance of United Nations Security Council resolutions barring it from conducting a ballistic missile program.
Does North Korea have nuclear weapons? Yes. North Korea has a small arsenal of small nuclear weapons as proven by its five nuclear tests. According to the Congressional Research Service, it is generally believed that North Korea has between 30 and 40 kilograms of separated plutonium, enough for at least half a dozen nuclear weapons. But other estimates range higher, the Institute for Science and International Security estimated in 2014 that North Korea could build 10 to 16 nuclear weapons.
Does North Korea have miniaturized nuclear warheads? No, but it is working toward its stated goal of placing a nuclear warhead small enough to be placed atop an ICBM that could target the United States. Last year North Korea conducted two nuclear tests it claimed were miniaturized hydrogen bombs. U.S. officials discounted the claim that the first test in January had been successful, however the second test in September produced the largest of the five nuclear tests it has conducted since 2006.
Where are the closest American troops? There are 28,500 American troops permanently stationed in South Korea as part of the U.S. security commitment to South Korea after the Korean War. There are there also 54,000 American troops in Japan, the largest number of American forces in Japan are stationed on the island of Okinawa.
What other countries in the region have nuclear weapons? North Korea is bordered by Russia and China, both countries have nuclear weapons arsenals. Russia currently has 1,796 nuclear warheads, a legacy from the Soviet Union's Cold War arsenal. China does not make available information about its nuclear weapons program, but various think tanks estimate it has 260 nuclear warheads. The Pentagon believes China has between 75 and 100 nuclear-capable ICBMs.
Can the United States defend against a North Korean missile attack? The United States has a layered missile defense system designed to track and intercept a missile launch from North Korea. It includes missile interceptors aboard Navy ships in the Pacific and large ground-based interceptors located in Alaska and California. However, the viability of the large interceptors has been routinely questioned since they became operational nearly a decade ago.
What is THAAD? The Terminal High Altitude Area Defense (THAAD) system is a missile defense shield designed to intercept short and medium range missiles. On Tuesday, the United States deployed THAAD to South Korea for the first time, a long-planned move agreed to last summer after a series of North Korean missile tests. The United States has also placed the THAAD system in Guam, which could be the maximum reach for some of North Korea's long-range missiles.