Sometime between noon and 4 pm Pacific Time, the Pentagon will attempt to intercept and destroy an intercontinental ballistic missile. The Pentagon has other systems designed to shoot down short-range and medium-range missiles but this is the first ever attempt to shoot down an ICBM. From ABC News:

The U.S. will launch an ICBM-class target from the Reagan Test Site on Kwajalein Atoll in the Republic of the Marshall Islands and a ground-based interceptor from Vandenberg Air Force Base in California. If successful, the “kill vehicle,” or intercept, will collide with the ICBM test target mid-course over the Pacific Ocean… This will be the 18th test of the ground-based interceptor. The last one, in June 2014, was the first success since 2008. The system is nine for 17 since 1999 with other types of target missiles. An ICBM target has never been tested before.

The Associated Press created this graphic showing the location of the ICBM and the interceptor. The “kill vehicle” does not have a warhead but uses its high-speed impact to destroy the target.

While today’s test was not set up in response to any particular action by North Korea, it is a significant part of the U.S. defense to limited ICBM strikes like the ones North Korea hopes to be able to carry out in the next few years. North Korea intends to keep improving its missiles until it can launch a nuclear warhead capable of reaching U.S. soil.

Earlier this month, North Korea launched a missile which flew for nearly 30 minutes and reached an altitude of over 1,200 miles. Because the missile was launched at a high angle it landed a few hundred miles away. However, the AP reported that if the missile had been launched at a shallower angle “analysts say, it could have flown much farther — estimates vary between 4,000 and 7,000 kilometers.” The outside estimate would place Alaska and Hawaii within striking distance.

It’s not clear when the Pentagon will reveal the results of today’s test. If they announce them later today, I’ll add an update below.

Update: Fox Business reports the test was a success: