The United States and South Korea are to hold a series of joint military exercises in response to the late March sinking of a South Korean warship, blamed on North Korea. The first drill is to begin Sunday in the Sea of Japan.  It is being called unprecedented in scope with 8,000 forces participating, 20 surface ships and submarines and about 200 fixed wing aircraft.

Aircraft carrier USS George Washington, arriving in Korean waters, is the centerpiece of a considerable four-day show of force off South Korea's east coast and in its skies.  The top brass of the U.S. Forces in Korea say the large-scale drill will highlight resolve to face any threat posed by North Korea.

Rear Admiral Kim Kyung-shik, of the South Korean joint chiefs of staff, puts it in even blunter terms.

"The purpose of this drill is to confirm the strong will of the US-South Korean alliance and to send a clear warning to North Korea," said Kyung-shik. "We are conducting this exercise to train in preparation for various military provocations by North Korea."

Another significant aspect of this exercise: for the first time, F-22 jets, with Stealth technology, will participate. Known as Raptors, they are considered the most advanced fighter aircraft of the U.S. Air Force.

South Korea had originally announced that the exercise would also take place in the Yellow Sea. China strongly objected. This joint drill will keep to waters off South Korea's east coast.

U.S. Army Major General John MacDonald says the Sea of Japan is most suitable for this particular drill, while the more controversial western waters will be the setting for future joint training.

"It has a capability that we're going to exercise very thoroughly on that side," said MacDonald.  "So we will have exercises in whichever sea that the ROK (South Korea) and the U.S. alliance decide to do, and you'll see that those come in the future."

The exercise also comes at a time when the intelligence communities in both the United States and South Korea are predicting ailing North Korean leader Kim Jong Il could act in an increasingly unpredictable way.  Some analysts believe the North Korean leader may endorse provocative military actions meant to glorify his relatively unknown youngest son (Kim Jong Un) to help legitimize his succession.

After a visit to the Demilitarized Zone with US Secretary of State Hillary Clinton and talks in Seoul with their South Korean counterpart, the U.S. Defense Secretary, Robert Gates, acknowledged sharing that concern.  "... it is something we have to be on the lookout for, to be vigilant, but also to be strong," said Gates.

South Korea's top defense officials acknowledge they are working with the  United States on contingencies in case of sudden change in the North - which they are terming "a strong possibility." Officials here, however, are quick to add that there is no clear indication such a change is imminent.