Breaking the predawn serenity, the areas just south of the 38th parallel were engulfed with roaring cannons and flames on June 25, 1950, as North Korea launched a coordinated attack from coast to coast with the backing of the Soviet Union and China.

Sixty-five years on, tension is omnipresent throughout the Demilitarized Zone, a 250-kilometer-long, 4-kilometer-wide strip set up after an armistice agreement separating the two Koreas. Antipodal to its name, it remains the world’s most heavily militarized frontier, brimming with landmines, artillery, watchtowers and soldiers from each side in a perennial face-off.

The two sides remain technically at war, as the three-year conflict ended in July 1953 in a truce, not a peace treaty.

Official data shows that 137,899 South Korean troops were killed in action while 450,742 were wounded. Some 215,000 North Korean soldiers were estimated to have died on top of the 303,000 injured.

More than 2.54 million South and North Korean civilians were killed, wounded or went missing during the war, though estimates vary. The U.S. lost about 37,000 soldiers, whereas about 114,000 Chinese troops were estimated to have been killed.

As much as the massive casualties, the Korean War left a legion of hardly healable scars on millions of people across the border.

Memories of separated loved ones, prisoners of war and abductees haunt their aging families in South Korea, while many veterans at home and elsewhere struggle to surmount the horrors of the battlefield.

Meanwhile, the awareness -- and longing -- for a reunification is increasingly eroding among more affluent and individualistic young generations. The widening gap between the two economies stokes concerns over the astronomical costs of a possible reintegration.

Predawn attack

The 38th parallel was set up as the border between the Koreas chiefly to allow the disarmament of the Japanese troops that occupied the peninsula from 1910-45, following the end of World War II.

A communist regime led by Kim Il-sung was established in the North under the supervision of the Soviet Union, while a separate government led by President Syngman Rhee took off in the South, overseen by the U.S.

When the Soviet Union withdrew from the peninsula in 1948, it left behind a well-armed and trained North Korean army. At the time of the U.S. pullout the next year, the South Korean military was ill-equipped and unprepared for a sudden invasion.

Furnished with a wide range of weaponry, including 242 T-34 tanks and 176 self-propelled guns, mostly from the Soviet Union, North Korean troops crossed the border, catching off guard their southern counterparts, half of whom were on leave over the weekend. The North Korean army numbered around 191,600, while the South Korean military had only some 94,000 personnel.

The North initially claimed that it was launching a counterattack in self-defense after the South invaded its territory. Yet hours after its attack, the U.N. Security Council issued condemnation, urging a halt to the hostilities and removal of its forces.

On June 27, the council adopted a resolution recommending its member states offer military assistance to the South, while U.S. President Harry Truman ordered the U.S. military to support the South, a pivotal point to contain communist expansion.

The U.N. Command was established on July 7, 1950. Gen. Douglas MacArthur was appointed as commander in chief of the U.N. forces in Korea. Sixteen countries including the U.S., the U.K. and Canada joined to fight for the South, with five additional states providing medical support.

Despite early defeats, the U.N. forces drove the North Korean troops back past the 38th parallel on Oct 18. The allied forces captured Pyongyang on Oct. 19 and advanced toward the Yalu River running along the North Korean-Chinese border, precipitating Chinese intervention.

Truce talks

Armistice negotiations began on July 10, 1951, and lasted about two years. Hostilities continued, while the talks ran into stumbling blocks such as a repatriation of prisoners and demarcating of the truce line.

Until the cease-fire was sealed on July 27, 1953, the U.N. and the communist forces held more than 760 meetings. Then came the Demilitarized Zone.

Though Rhee initially refused to endorse the accord, Seoul and Washington clinched a mutual defense treaty to jointly deal with the military tensions on the peninsula on Oct. 1, which allowed U.S. forces to be stationed in the South as a deterrent against another North Korean invasion. The U.S. maintains 28,500 troops here currently.

Deep wounds

More than six decades on, tension remains high on the peninsula as the sides have since engaged in a spate of military clashes.

The North torpedoed the South Korean corvette Cheonan in the West Sea in March 2010, killing 46 sailors, and months later shelled Yeonpyeongdo Island. Pyongyang’s denial of responsibility and demand for a lifting of the bilateral sanctions that the then-President Lee Myung-bak imposed to forbid cross-border trade, investment, travel and other exchanges are some of flashpoints between the two Koreas.

Further aggravating cross-border tension is Pyongyang’s nuclear and missile programs. It conducted atomic tests in 2006, 2009 and 2013 and is beefing up its capabilities by seeking to acquire the technology to miniaturize warheads to mount on missiles.

The ongoing territorial division has left deep wounds on South Koreans whose family members failed to come with them during the war, were kidnapped by North Korean agents or taken as prisoners of war.

According to the Unification Ministry, only 66,843 of the 129,688 South Koreans registered since 1988 remain alive as of May 31, meaning that more than 2,000 have died each year.

Tens of thousands of South Korean soldiers are believed to have been taken prisoner by North Korea, some 500 of which Seoul thinks are still alive. About 80 prisoners of war fled to the South, more than 30 of them have since died. Government statistics say that another 80,000 South Koreans were abducted to the North between 1952 and 1953.

Far-fetched dream

Reunification has been a cherished dream among Korean people and a foremost goal enshrined in the country’s constitution.

Last year, President Park Geun-hye set unification as the centerpiece of her second-year presidency, saying a unified Korea would bring about a “bonanza” to not only the peninsula but the region and the world, and a chance for the national economy to take a leap forward.

Yet the long-held national aspiration, preserved in the popular song “Our Wish is Unification,” is rapidly fading among younger South Koreans. A recent poll by Gallup Korea showed that only 64 percent of the 1,000 respondents answered accurately when asked for the year of the outbreak of the Korean War.

Aside from the heated debate on unification, many people here remain wary of its potentially immense costs and disorder. North Korea fears it would mean the demise of its iron-fisted regime and absorption into its wealthy neighbor.

A 2012 study commissioned by the Unification Ministry put unification costs at between 55 trillion won and 249 trillion won ($49.6 billion to $224.5 billion), based on a 2030 price trajectory, assuming that it takes place within the next 20 years and is a peaceful transition. The upper end of that range is about one-fifth of the South’s 2011 gross domestic product.

The ministry in charge of inter-Korean affairs, such as humanitarian aid and the Gaeseong Industrial Complex, aims to collect up to 50 trillion won by 2030 under the South-North Cooperation Fund from public donations and state coffers.

By Shin Hyon-hee (heeshin@heraldcorp.com)