The restrictions were a blessing in disguise as it allowed the troops to develop expertise at the individual and small-unit levels, Anderson said.
"This is the first time to really bring them all together, over 1,000 people," he said.
South Korean General Kim Nam-hoon, deputy commander of the combined division, said the troops would improve their ability to operate together through joint drills.
Many large exercises were cancelled starting in 2018 as then-U.S. President Donald Trump tried to persuade North Korean leader Kim Jong Un to give up his nuclear weapons. COVID later disrupted more drills.
A former senior defence official told Reuters that in many cases U.S. and South Korean forces continued to train but did not publicize it.