The drills could trigger a response from North Korea, which has long portrayed the exercises as invasion rehearsals.

The drills could trigger a response from North Korea, which has long portrayed the exercises as invasion rehearsals.

The drills could trigger a response from North Korea, which has used previous exercises as a pretext for weapons tests.

The United States and South Korea kicked off their annual summertime joint military exercise on Monday, amid efforts by Seoul to improve relations with North Korea.