PENTAGON -- When it comes to North Korea, the U.S. military has been "locked and loaded" for years. The motto of the 28,000 American troops in South Korea -- as well as long range bombers based 2,000 miles away on Guam -- is "Fight Tonight," meaning be ready for an attack that could come with little or no warning.

They will become even more ready later this month when 3,000 more troops arrive in South Korea for one of several exercises held each year.

Ballistic missile defenses in South Korea, Guam and the U.S. are kept on alert in case North Korea launches a missile in their direction.

The U.S. military has long been "locked and loaded" when it comes to North Korea. CBS News

On Guam, local officials took the added precaution of putting out a bulletin explaining what to do in the event of nuclear attack: "Do not look at the flash or fireball -- it can blind you."

Officials say if the North fired a missile at the American homeland or a U.S. military base overseas, the Pentagon would first try to shoot it down. Then second, the U.S. would retaliate with an attack of its own, perhaps with a cyber weapon. In the unlikely event the North used a nuclear weapon, the U.S. would mount a much more devastating attack

The Pentagon also has options for a preemptive strike to knock out North Korea's nuclear weapons facilities. But retired Adm. James Winnefeld, formerly the No. 2 man in uniform, says that would be a long shot.

"It's a very difficult target," Winnefeld told CBS News. "It's a very mountainous country. They have buried much of what they do. It's very hard to locate. So it's a very risky operation to try to take all of those diverse and dispersed targets out at one time."

President Trump tweeted "military solutions are now fully in place." But Pentagon officials insist no action is imminent and that the only real solution is a diplomatic one.