What to know about North Korea and its weapons programs

PHOTO: In this Saturday, Oct. 10, 2015, photo, missiles and rockets are paraded in Pyongyang, North Korea during the 70th anniversary celebrations of its ruling partys creation.PlayWong Maye-E/AP Photo
WATCH North Korea fires new round of ballistic missiles

After North Korea’s second ICBM test, here is what we know about the country’s nuclear weapons program.

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 to 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. Panmunjom 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 it falls to the earth on its own toward 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.

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. ICBMs 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?
Yes. On July 4, North Korea conducted its first ICBM test, using a new two-stage missile similar to the KN-17 that had achieved a high altitude when tested in mid-May. Before that point, there had been little indication that nation was close to testing this type of missile. The country conducted a second ICBM test on July 28. That missile, which traveled, 621 miles laterally and was airborne for 45 minutes, was the longest flight of a ballistic missile in North Korea's history, according to the Pentagon.

How many missiles does North Korea possess?
The Pentagon 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?
Yes. According to the South Korean Joint Chiefs of Staff, North Korea's recently tested ICBM can traveled 2,300 miles into space. Experts fear that if they angled the trajectory of that missile, it could potentially travel as far as Washington, D.C., or New York.

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 44 and 66 pounds 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 which 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. In late May, the Missile Defense Agency successfully tested an interceptor that targeted an ICBM test missile fired from Kwajalein Atoll in the South Pacific.

What is THAAD?
The Terminal High Altitude Area Defense (THAAD) system is a missile defense shield designed to intercept short and medium range missiles. In April, 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.

ABC News' Jack Arnholz and Elizabeth McLaughlin contributed to this report.