In any future war on the Korean Peninsula, U.S. and South Korean forces would encounter a familiar foe: the Korean People’s Army (KPA) 105th Armored Division. Equipped with North Korea’s most modern tanks and armored vehicles, the 105th Division’s mission is to rapidly exploit any breakthrough in the lines and drive deep into the heart of South Korea. The division traces its lineage to the first Korean War, when its Soviet-made tanks panicked ill-prepared U.S. troops and very nearly achieved total victory.

The end of the Second World War saw Korea, formerly a Japanese colony, partitioned between the victorious Allies. The peninsula was divided at the 38th parallel, with Soviet forces occupying the northern half and the United States and Western allies occupying the southern half. U.S. and Soviet-backed governments sprung up in both northern and southern sectors. The Soviet Union began training and equipping the new Korean People’s Army, a force that quickly grew to include ten infantry divisions and an armored brigade, the 105th. In June 1950, KPA forces flooded south, attacking the lightly armed and equipped Republic of Korea Army.

The 105th Armored Brigade traced its origins to the 15th Tank Training Regiment, a tank unit formed by the Red Army in 1948 and commanded by Senior Colonel Yu Kyong Su, a former lieutenant in the Red Army and brother-in-law to North Korean leader Kim Il Sung’s wife. Many soldiers of the 15th Regiment were war veterans who had already served in the Soviet and Chinese armies. This early force rapidly grew from a small cadre of Soviet and North Korean personnel and two T-34 tanks to become the 105th Armored Brigade with 120 T-34 tanks.

The brigade was envisioned from the outset as the spearhead of a KPA drive to reunify the peninsula by force and was equipped with the T-34/85 tank. The last model of the famed T-34 line, the T-34/85 had the larger 85mm ZIS-S-53 anti-aircraft/anti-tank gun, and was the mainstay of the Red Army as it swept into Berlin just five years earlier. The T-34/85 was considerably less armored than its American contemporary, the M26 Pershing, but could penetrate the Pershing anywhere but the heavily armored front glacis at 1,000 yards.

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According to noted tank authority Steven Zaloga, the 105th Brigade was made up of three tank battalions, the 107th, 109th, and 203rd, each with forty tanks. Another battalion, the 308th Armored, was equipped with sixteen SU-76 self-propelled guns, and infantry support was provided by the 206th Motorized Infantry Regiment.

Facing the 105th Armored Brigade was a South Korean army trained and equipped more like a European gendarme than a combat-ready force. The Republic of Korea Army was primarily an infantry force, not only without a corresponding armored unit but without any armor at all. Instead, the ROK and its American advisors had thirty-seven obsolete M8 Greyhound armored cars and 140 obsolete 57mm towed anti-tank guns. Infantry forces were generously equipped with 1,900 2.36-inch bazookas, but these weapons were already outdated in 1944, let alone 1950, and were a poor match for the T-34/85’s armor.

The 105th Brigade did not fight as a cohesive force but rather had its regiments doled out to provide armored support to KPA infantry divisions. The three regiments participated in attacks that crushed the ROK 1st and 7th Infantry Divisions, and although tanks were damaged by improvised anti-tank weapons, none were actually lost. North Korean tanks swept through Seoul, capturing the capital city on the fourth day of the war, but a lack of engineering support meant kept KPA tanks on the north side of the Han River until July 3rd. The brigade was elevated to division status and renamed the 105th “Seoul” Armored Division as a result.

Advancing down the peninsula, the 105th Division encountered its first American combat force. Task Force Smith, airlifted from Japan, consisted of the understrength 1st battalion, 21st Infantry Regiment of the 24th Infantry Division. A garrison division that never expected to see large scale combat, the 24th was ill-equipped with poorly maintained weapons. The task force’s anti-tank weapons amounted to just two 75mm recoilless rifles and six 2.36-inch bazookas, with 4.2-inch mortars and field artillery in support.

Against the Americans of Task Force Smith rolled thirty-three T-34s of the 107th Armored Regiment, followed by the 16th and 18th Regiments of the KPA 4th Infantry Division. The task force was beaten decisively and panicked U.S. soldiers fell back against the unstoppable tank force. For all the U.S. Army’s prowess, the task force was only able to disable four enemy tanks—two permanently—for a loss of 150 killed and wounded. Task Force Smith’s failure would later become a pointed reminder of how quickly an army can lose its fighting edge.

The 105th Armored Division continued its advance south, harried by United Nations airpower. M24 Chaffee light tanks and a small number of heavier M26 Pershings were committed to the fight but suffered from mechanical breakdowns. At the Pusan Perimeter, the division’s tanks were doled out in packets to support infantry attacks rather than committed in a single decisive attack. Although the 105th had suffered few combat losses, the drive south had damaged and worn many of the division’s tanks.

Meanwhile, UN forces were gradually receiving heavier weapons, both M-26 Pershings and 3.5-inch bazookas. At Obong-Ni Ridge, four M-26s of the Marine Corps 1st Tank Battalion destroyed three T-35/85s with zero losses. North of Tabu-dong, U.S. Army infantry and Pershing tanks destroyed thirteen T-34s and five SU-76s of the 107th Armored Regiment in two days of fighting. A final September push by the KPA against the Pusan Perimeter involved 100 tanks manned with inferior replacement and trainee crews—and the offensive was unsuccessful.

The U.S. Army and Marine Corps landing at Inchon cut off KPA invasion forces besieging Pusan, and the tanks of the 105th Division ended up fighting a number of holding actions against the counteroffensive from Pusan, often in small numbers. By September, the UN estimated North Korea had lost 239 tanks to the UN’s sixty tanks. North Korea’s armored corps, used to great effect since the initial invasion, had been completely destroyed.

The division was reorganized in 1951 as the 105th Mechanized Division but avoided combat for the rest of the war. By the early 1960s, the division had been reinstated as a tank formation and named the 105th Seoul Guards Armored Division. Today, the 105th is generally acknowledged to be the KPA’s most prestigious and modern conventional nit. The division is structured around two tank brigades and one mechanized infantry brigade and is part of the 820th Armored Corps. The division’s primary main battle tank is the Pokpung-ho “Storm" tank.

In the event of war the 105th would once again charge south, exploiting any breakthrough in ROK Army lines to make a dash towards Seoul and beyond. Unlike the last war, the 105th would likely fight as a single cohesive force. While the feasibility of such an invasion is up for debate, the 105th Seoul Guards Armored Division is still likely one of the most capable and prestigious tank units in Asia, with a storied past to live up to in any future war.

Kyle Mizokami is a defense and national-security writer based in San Francisco who has appeared in the Diplomat, Foreign Policy, War is Boring and the Daily Beast. In 2009 he cofounded the defense and security blog Japan Security Watch. You can follow him on Twitter: @KyleMizokami.

Image: Reuters