US, South Korea prepare for joint military exercise amid heightened tensions

— -- U.S. and South Korean forces are preparing for a joint military exercise just weeks after North Korean leader Kim Jong Un threatened to launch missiles toward Guam.

For months, the U.S. and South Korea have been planning for Ulchi Freedom Guardian, an annual exercise that will involve 14,500 U.S. service members stationed on the Korean Peninsula and an additional 3,000 who will travel to participate. It is a "computer simulated defensive exercise designed to enhance readiness, protect the region and maintain stability on the Korean peninsula," the Pentagon said on Friday.

The exercise, which begins on Monday, will occur amidst heightened rhetoric between Kim and President Donald Trump over the country's nuclear and ballistic missile programs.

On August 8, Trump threatened North Korea with "fire and fury like the world has never seen," touching off a war of words between the two governments.

Kim said he would consider sending missiles into the waters off the coast of Guam in "mid-August." Guam is a U.S. island territory that is home to two American military bases.

But, after reviewing those plans, Kim ultimately decided he would “watch a little more the foolish and stupid conduct of the Yankees," seeming to walk back an imminent threat to the island and de-escalating tensions on the Peninsula -- at least for now.

In the week following the conclusion of Ulchi Freedom Guardian in 2016, North Korea conducted its fifth nuclear test. After this year's exercise concludes, the U.S. will most certainly be keeping a close eye on what the regime chooses to do.

Several U.S. officials told ABC News recently that the U.S. has not seen any activity in North Korea that would indicate an imminent missile launch. North Korea has already launched eleven ballistic missile tests so far in 2017.

As was the case in 2016, the North Koreans are expected to be informed of the "non-provocative" nature of Ulchi Freedom Guardian prior to its start.

In March, the U.S. and South Korea conducted another annual joint military exercise called Foal Eagle, which included air, naval, and special operations field exercises. In response to that exercise, North Korea threatened a "merciless attack."

There are more than 28,000 U.S. service members stationed in South Korea. Their motto is "Fight Tonight," reflecting their commitment to help defend South Korea from North Korean aggression at a moment's notice.

"While our State Department is making every effort to resolve this global threat through diplomatic means, it must be noted that the combined allied militaries now possess the most precise, rehearsed and robust defensive and offensive capabilities on earth," Defense Secretary James Mattis said last week. "The DPRK regime's actions will continue to be grossly overmatched by ours and would lose any arms race or conflict it initiates."