SEOUL — The surprise changes in the hierarchy of North Korea's military appear to have slightly rattled officials in rival South Korea.
South Korea is acknowledging it has put its forces on a higher state of alert.
Kim Min-seok, a spokesman at the Ministry of National Defense, says the readiness posture has been "slightly raised" and the military is "analyzing carefully what is happening in North Korea" after various surprise announcements from Pyongyang this week. He adds that discussions are underway on whether there is anything South Korean forces should be prepared for, in view of the reported changes and what they are observing.
The announced personnel and title changes in Pyongyang by the reclusive and opaque government have generated headlines and widespread speculation in recent days.
A veteran military chief, vice marshal Ri Yong Ho, was stripped of all of his posts. "Illness" was given as the reason in the Monday announcement, which said the decision had come at what was apparently a hastily called meeting of the political bureau of the workers' party central committee.
A day later there was an equally sparse announcement that a little-known general, Hyon Yong Chol, had replaced Ri.
Another surprise followed on Wednesday when leader Kim Jong Un was declared a marshal of North Korea.
Ri, who was also army general staff chief, early last month had issued an ultimatum against South Korea. He declared that Seoul would face a "merciless sacred war" unless it apologized for perceived insults.
Little more than a month before that threat, Pyongyang had announced it was preparing a "special operation" against Seoul.
South Korean official sources say American forces increased gathering of aerial intelligence over North Korea, this week, but have not detected any significant changes in military movements.
Jennifer Buschick, a spokesperson for the U.S. forces in South Korea, says: "As a matter of policy we do not discuss our security posture. We continue to monitor the situation with our Republic of Korea counterparts. The commander continually assesses and makes adjustments as necessary for the protection of our forces."
Professor Kim Yeon-soo at South Korea's National Defense University says the government in Seoul is reacting more prudently than it might have in past years.
He says increasing the readiness posture is in line with the government's greater scrutiny of activities in the North since the sinking of the Cheonan naval vessel and the shelling of Yeongpyeong island, which both occurred in 2010.
Some analysts contend an internal power struggle is now likely underway in Pyongyang. Others discount that, saying all of this may be nothing more than a young leader prudently proceeding to put his own stamp on the state apparatus.
Professor Kim says it is difficult to make any conclusions because no internal conflicts are evident.
He says it appears North Korea's military is stable and there is solidarity among Pyongyang's elite. Kim says he thinks North Korea is beginning to follow China's path of reform for its long-term survival and Beijing is pushing Pyongyang to reform and open to the outside world.
The two Koreas have no diplomatic relations. A three-year Korean civil war in the early 1950's ended inconclusively. During the devastating conflict, China backed North Korea while the United States - accompanied by United Nations forces - fought on South Korea's side.
North Korea maintains an army with more than one million troops on active duty. South Korea has about 650,000 regular forces allied with more than 28,000 American military personnel stationed in the country.