CAMP RED CLOUD -- When millions of Koreans take to the roads and rails to visit families from one end of the country to the other later this week, they'll be observing one of their biggest national holidays, Chuseok.
It's the nation's annual autumn harvest festival and falls this year on Sept. 27, but the overall holiday spans four days, Sept. 26 through 29. Most Korean employees on U.S. military installations in Korea will be off Sept. 28 and 29, giving them a four-day weekend.
Chuseok is considered Korea's most important holiday, according to the Korean government's Korea Tourism Organization (KTO) website. Chuseok and Seollal -- Korea's observance of Lunar New Year -- are the nation's two biggest holidays.
During Chuseok many Korean families gather and give thanks for the year's harvest and hold rituals that honor their ancestors.
Through much of Korea's history, Koreans saw harvest crops as a blessing that owes to one's ancestors. Korean Christian families typically do not perform rituals associated with ancestor worship, but do hold a Chuseok family gathering. Chuseok is often likened to American Thanksgiving.
During Chuseok, nearly all government offices and most businesses are closed. City streets can seem all but deserted.
Trains and buses are jammed and the nation's highways carpeted in bumper-to-bumper traffic as about three-fourths of Korea's population fans out across the country to visit relatives. They enjoy traditional foods and games, and make ritual visits to their family burial sites.
Chuseok can be thought of as having two main phases.
There's the long holiday weekend built around Chuseok Day itself, of course, but also the weeks of intense pre-holiday scrambling.
Koreans hurry to buy hard-to-get train and bus tickets well in advance. They buy and cook traditional Chuseok foods. And there's a big holiday surge in buying and sending Chuseok gifts.
For some Koreans there's even a preliminary trip -- sometimes at long distances -- to trim grass and pull weeds at family gravesites for the rituals that will later be performed during Chuseok itself.
Other families choose to wait until the holiday to get the gravesites ready. The preparation, regardless of when it's done, is called "beolcho."
But there's plenty else to do before Chuseok arrives.
There's much buying of gifts to be given to relatives and business associates at Chuseok.
And it's an especially busy time for the country's postal system and its home delivery businesses as families send Chuseok gifts to relatives.
But for all the bustle that goes into the run-up to Chuseok, there's nothing quite like the arrival of the holiday itself.
It's most obvious sign is that cities and towns can seem abruptly emptied of people.
Where is everybody? Many are bumper-to-bumper deep in one big traffic jam that eventually overspreads the entire country.
Motorists blanket the highways in trips that on Chuseok can take two and three times longer than they would were it not a holiday.
Also jammed with Chuseok travelers are the country's railroad stations and bus terminals.
Train and express bus tickets for Chuseok travel are in such demand they can sell out a month ahead of time. Buying of train tickets online has been so heavy at Chuseok season it's sometimes crashed the computer system. Those who try to buy at railroad ticket windows face long, slow-moving lines.
On Chuseok day itself, families gather at home and perform several acts, not necessarily in a set order.
They tidy family gravesites if they hadn't done so weeks earlier.
Typically, they then hold an indoor family ceremony, called "charye," in which they honor their ancestors' memory.
This service is followed by the traditional Chuseok meal, which is notorious for the long hours of painstaking cooking and other kitchen work Korean women typically perform in preparing it.
It's after all this that some families go to family gravesites and there, in a ritual called "seongmyo," render a formal bow of respect to their ancestors.
Some Koreans, however, are moving away from traditional Chuseok practices. A growing number are skipping Chuseok observance entirely and using the days off for leisure trips, often to places outside Korea.
Some families hire landscaping services to clear weeds and trim grass at gravesites. Some order Chuseok food from catering businesses.
Chuseok also sees a surge in movie-going, with the holiday affording Koreans a chance to get to the theaters.
But for those millions of Koreans who keep to the more traditional observance, there comes the second and final holiday challenge, the return trip.
Trains, buses, roads, highways and city streets are once again congested, as three-fourths of the nation's populace, their preparations and get-togethers over for another year, press their way home.