The outgoing commander of U.S. military forces on the Korean Peninsula said Tuesday that North Korea’s youthful and enigmatic leader, Kim Jong Un, has successfully consolidated power, even as he has dashed international hopes that he might turn out to be a reformer.

“It’s clear to me that he’s in charge up there,” said Army Gen. James D. Thurman, who is retiring and will leave his post this week as the commander of 28,500 U.S. troops in South Korea. “We’ve got to keep a close watch on him, every day, and that’s what we try to do.”

Thurman made his comments on the same day that South Korea celebrated the founding of its armed forces with the country’s biggest military parade in a decade. About 11,000 South Korean troops marched through downtown Seoul and showed off tanks, advanced artillery and a new cruise missile that is capable of striking anywhere in North Korea.

The parade was attended by a brass-packed roster of U.S. national security officials, including, in addition to Thurman, Defense Secretary Chuck Hagel; Army Gen. Martin Dempsey, the chairman of the Joint Chiefs of Staff; and Adm. Samuel Locklear, the chief of the U.S. Pacific Command.

On Wednesday, Thurman is scheduled to hand over command of U.S. forces in Korea to Army Gen. Curtis Scaparrotti, a former high-ranking commander in Afghanistan who most recently served as director of the Joint Staff at the Pentagon.

Tensions have subsided in the region since North Korea tested a nuclear bomb in February and Kim threatened attacks on U.S. military bases in South Korea and elsewhere in Asia. Thurman said one lesson from that period was the need to take such threats seriously without overreacting in public.

“One of the things that we were able to do is remain calm and confident and not get excited,” he told reporters. “It is very important, from an alliance perspective, to assure the Korean people here that they’re going to be okay and that things are going to work out fine.”

Kim, who is believed to be 30 years old, assumed power after his father, Kim Jong Il, died in December 2011. Although little was known about him, U.S. officials were guardedly optimistic that his boarding school education in Switzerland and fondness for Western culture — he is a big fan of NBA basketball and Disney entertainment — would lead to a thaw in relations with Washington and Seoul. “I was a bit optimistic that we would see a change in behavior,” Thurman said.

Other U.S. military and defense officials said Kim’s personality and intentions are still hard to pin down.

“He is definitely in charge, but he is young, impetuous and unpredictable,” said a senior defense official who studies North Korea closely and spoke on the condition of anonymity to give a frank assessment. “We’ve been looking at him for a little over 18 months now, but we still don’t understand his intent.”