The two allies plan to continue the Maritime Counter Special Operations Exercise (MCSOFEX) through Friday in the East Sea and the Yellow Sea.

As reported over the weekend, the drill involves the U.S. 7th Fleet's aircraft carrier USS Ronald Reagan (CVN-76) and two Arleigh Burke-class destroyers - the USS Stethem (DDG-63) and the USS Mustin (DDG-89). The carrier strike group will train with South Korean warships and other defense assets, such as the Sejong the Great Aegis ship and P-3 Orion anti-submarine aircraft in the East Sea.

And while details of the drill were well-known in advance, what was reported for the first time overnight from Yonhap is that a unit of U.S. special forces tasked with carrying out "decapitation" operations is also aboard a nuclear-powered submarine in the group, according to a defense source. So far, little else is known about why said decapitation team is on location, or whether it will be put into use, although it presence may explain Trump's "calm before the storm" comment that beffudled the media two weeks ago.