The U.S. and South Korean militaries began their annual joint exercises on April 1, following a monthlong delay for the Winter Olympics and while North-South talks took place.
The Foal Eagle field exercise will run for four weeks, both countries have said, meaning they will last about half the time as last year’s maneuvers.
They will involve combined ground, air, naval, and special operations troops.
The computer-simulated Key Resolve exercise will begin in mid-April and last for about two weeks, officials said.
A Pentagon spokesman said the drills will feature about 23,700 U.S. troops and 300,000 South Korean forces.
North Korea in the past has assailed U.S.-South Korean military drills as preparations for an invasion, but has not raised such objections this time.
North Korean leader Kim Jong Un in March told a visiting South Korean delegation that he "understands" the situation, South Korean officials said.
A summit between Kim and U.S. President Donald Trump is anticipated by the end of May amid global diplomatic efforts to resolve the standoff over the North's nuclear program.
Pyongyang and Seoul are also scheduled on April 27 to hold a summit, their first in more than a decade.