North Korea is crazy about nukes. While the country's reported capability to produce a nuclear warhead small enough to fit in a missile is new, it's obsession with nuclear weapons is not.

North Korea has been hellbent on developing a dependable nuclear stockpile since the Cold War era, and North Korean leader Kim Jong Un has ratcheted up that effort since taking power in 2011. The question now is whether the war of words between President Trump and Kim could turn real.

While we wait to see what happens, here's a refresher on North Korea's long-running nuclear obsession.

How long has North Korea been working on its nuclear weapons?

North Korea's interest in nuclear weapons dates back to the 1960s, The Washington Post reports. That's when Kim Il Sung, the founder of North Korea and Kim Jong Un's grandfather, approached his key ally, the Soviet Union, for assistance in building a nuclear weapons program. Moscow instead pushed North Korea to sign on to the Nuclear Non-Proliferation Treaty. One year after joining the treaty in 1985, which barred North Korea from making nuclear weapons, the country's nuclear reactor in Yongbyon was up and running.

Tensions flared in the '90s, when North Korea wavered on its commitment to the treaty and U.S. officials suspected something was going on with the country's nuclear weapons program. By 2003, North Korea pulled out of the treaty.

In 2005, North Korea announced it had nuclear weapons. In October 2006, North Korea announced its first successful nuclear test.

There have been four successful tests since then and numerous attempts by the global community to halt North Korea's nuclear program.

Has North Korea actually been all that successful?

Recent reports suggest that North Korea recently hit a landmark moment in its nuclear weapon development: It can now produce nuclear warheads small enough to fit inside missiles. This development is key to North Korea's ability to strike a country like the United States with a nuclear weapon.

On top of that, North Korea is "outpacing expectations" in its effort to make a missile that could hit the U.S. mainland, The Washington Post reported. North Korea claims it could already reach the mainland, but analysts suspect it could only reach Alaska or Hawaii.

A recent assessment by the U.S. Defense Intelligence Agency raised previous estimates of how many bombs North Korea has in its arsenal to as many as 60 weapons. Moreover, each of North Korea's nuclear tests over the last decade has been "more powerful than the last," The New York Times reported.

A sixth test appears to be in the works.

Why nuclear weapons?

North Korean leader Kim Jong Un sees the most devastating weapon known to man as "the only way the North can guarantee its security and develop its economy," The New York Times reported:

His government has argued that it needs nuclear arms to protect itself from being toppled like others who gave up weapons of mass destruction; the state news media has pointed to Col. Muammar el-Qaddafi and Saddam Hussein.

But the North has also said it hopes to use nuclear arms to force the world, including the United States, to accept it as a full member of the international community on its terms — just as Washington eventually recognized China after it became a nuclear power. [The New York Times]

Historically, the Cold War — a period when many countries' interest in nuclear weapons was piqued — also plays a factor in North Korea's long-lasting focus on nuclear weapons. North Korea was left in a vulnerable position when the Soviet Union collapsed, and enlisted the help of former Soviet engineers to develop its nuclear program.

North Korea's confidence blossomed as the international community grew wary of its nuclear capabilities. The Washington Post explains, "The nuclear program gave North Korea international clout far bigger than its stagnating economy and diplomatic isolation would normally afford."

Why has its nuclear activity intensified in recent years?

Kim Jong Un.

North Korea's nuclear program grew "relatively slowly" while Kim Jong Il, father to the current leader, was in power from 1994 to 2011, The Washington Post reports. But when Kim Jong Un took over in 2011, the pace picked up. North Korea in recent years has poured resources into its nuclear weapons program and the effort has paid off.

North Korea says it's conducted five successful nuclear tests: first in 2006, then in 2009, 2013, and twice in 2016. Of those five tests, three have been conducted while Kim Jong Un was in power. The New York Times reported that under Kim Jong Un's leadership, North Korea has also carried out 80 missile tests — "more than twice as many as under his father and grandfather combined."

What are the odds of North Korea putting its obsession to rest?

Slim to none. Kim Jong Un has kept his eyes firmly on developing nuclear weapons, despite sanctions and deals offering security and economic assistance.

Aside from Kim's conviction that the nuclear program will win him and his country the recognition he's been seeking, The New York Times pointed out that Kim's reputation is also tied up in the program because he's so closely involved. The Economist noted that Kim Jong Un has called his nuclear weapons program his "treasured sword of justice." If he were to end it, he might lose face with the military, always a dangerous thing for a totalitarian ruler.

Besides, even when North Korea has agreed to deals to cease its nuclear weapons production in the past, it's inevitably failed to hold up its end of the bargain. This happened in a 1994 deal between former President Bill Clinton and Kim Jong Il, and again in 2005.

So, what are the odds North Korea is actually going to use these weapons it's been stockpiling?

With President Trump seemingly ad-libbing threats, it's hard to say. North Korea is known for its over-the-top bellicosity, but its recent threat to attack the U.S. territory of Guam — made in response to Trump's threat to rain down "fire and fury" on North Korea — was notably specific.

But there's always the chance that Kim Jong Un will just keep holding his weapons over the world's head instead of actually using them, The Washington Post notes:

The brutality of the North Korean regime is notorious. [...]

But there is little sign that Kim is suicidal. The North Korean regime is probably well aware that it could not survive a nuclear war with the United States — it is outmatched in terms of both nuclear and conventional weapons. Instead, North Korea's weapons seem to be a bargaining chip. [The Washington Post]

If Trump strikes first though, North Korea certainly has the weapons to retaliate.